diff --git a/lib/jasmine-core/jasmine.js b/lib/jasmine-core/jasmine.js
index fa9938e6..a0ba7a6b 100644
--- a/lib/jasmine-core/jasmine.js
+++ b/lib/jasmine-core/jasmine.js
@@ -4925,117 +4925,116 @@ getJasmineRequireObj().toBeResolvedTo = function(j$) {
 };
 
 getJasmineRequireObj().DiffBuilder = function(j$) {
-  return function DiffBuilder(config) {
-    const prettyPrinter =
-      (config || {}).prettyPrinter || j$.makePrettyPrinter();
-    const mismatches = new j$.MismatchTree();
-    let path = new j$.ObjectPath();
-    let actualRoot = undefined;
-    let expectedRoot = undefined;
+  class DiffBuilder {
+    constructor(config) {
+      this.prettyPrinter_ =
+        (config || {}).prettyPrinter || j$.makePrettyPrinter();
+      this.mismatches_ = new j$.MismatchTree();
+      this.path_ = new j$.ObjectPath();
+      this.actualRoot_ = undefined;
+      this.expectedRoot_ = undefined;
+    }
 
-    return {
-      setRoots: function(actual, expected) {
-        actualRoot = actual;
-        expectedRoot = expected;
-      },
+    setRoots(actual, expected) {
+      this.actualRoot_ = actual;
+      this.expectedRoot_ = expected;
+    }
 
-      recordMismatch: function(formatter) {
-        mismatches.add(path, formatter);
-      },
+    recordMismatch(formatter) {
+      this.mismatches_.add(this.path_, formatter);
+    }
 
-      getMessage: function() {
-        const messages = [];
+    getMessage() {
+      const messages = [];
 
-        mismatches.traverse(function(path, isLeaf, formatter) {
-          const { actual, expected } = dereferencePath(
-            path,
-            actualRoot,
-            expectedRoot,
-            prettyPrinter
-          );
-
-          if (formatter) {
-            messages.push(formatter(actual, expected, path, prettyPrinter));
-            return true;
-          }
-
-          const actualCustom = prettyPrinter.customFormat_(actual);
-          const expectedCustom = prettyPrinter.customFormat_(expected);
-          const useCustom = !(
-            j$.util.isUndefined(actualCustom) &&
-            j$.util.isUndefined(expectedCustom)
-          );
-
-          if (useCustom) {
-            messages.push(
-              wrapPrettyPrinted(actualCustom, expectedCustom, path)
-            );
-            return false; // don't recurse further
-          }
-
-          if (isLeaf) {
-            messages.push(
-              defaultFormatter(actual, expected, path, prettyPrinter)
-            );
-          }
+      this.mismatches_.traverse((path, isLeaf, formatter) => {
+        const { actual, expected } = this.dereferencePath_(path);
 
+        if (formatter) {
+          messages.push(formatter(actual, expected, path, this.prettyPrinter_));
           return true;
-        });
+        }
 
-        return messages.join('\n');
-      },
+        const actualCustom = this.prettyPrinter_.customFormat_(actual);
+        const expectedCustom = this.prettyPrinter_.customFormat_(expected);
+        const useCustom = !(
+          j$.util.isUndefined(actualCustom) &&
+          j$.util.isUndefined(expectedCustom)
+        );
 
-      withPath: function(pathComponent, block) {
-        const oldPath = path;
-        path = path.add(pathComponent);
-        block();
-        path = oldPath;
+        if (useCustom) {
+          messages.push(wrapPrettyPrinted(actualCustom, expectedCustom, path));
+          return false; // don't recurse further
+        }
+
+        if (isLeaf) {
+          messages.push(this.defaultFormatter_(actual, expected, path));
+        }
+
+        return true;
+      });
+
+      return messages.join('\n');
+    }
+
+    withPath(pathComponent, block) {
+      const oldPath = this.path_;
+      this.path_ = this.path_.add(pathComponent);
+      block();
+      this.path_ = oldPath;
+    }
+
+    dereferencePath_(objectPath) {
+      let actual = this.actualRoot_;
+      let expected = this.expectedRoot_;
+
+      const handleAsymmetricExpected = () => {
+        if (
+          j$.isAsymmetricEqualityTester_(expected) &&
+          j$.isFunction_(expected.valuesForDiff_)
+        ) {
+          const asymmetricResult = expected.valuesForDiff_(
+            actual,
+            this.prettyPrinter_
+          );
+          expected = asymmetricResult.self;
+          actual = asymmetricResult.other;
+        }
+      };
+
+      handleAsymmetricExpected();
+
+      for (const pc of objectPath.components) {
+        actual = actual[pc];
+        expected = expected[pc];
+        handleAsymmetricExpected();
       }
-    };
 
-    function defaultFormatter(actual, expected, path, prettyPrinter) {
+      return { actual: actual, expected: expected };
+    }
+
+    defaultFormatter_(actual, expected, path) {
       return wrapPrettyPrinted(
-        prettyPrinter(actual),
-        prettyPrinter(expected),
+        this.prettyPrinter_(actual),
+        this.prettyPrinter_(expected),
         path
       );
     }
-
-    function wrapPrettyPrinted(actual, expected, path) {
-      return (
-        'Expected ' +
-        path +
-        (path.depth() ? ' = ' : '') +
-        actual +
-        ' to equal ' +
-        expected +
-        '.'
-      );
-    }
-  };
-
-  function dereferencePath(objectPath, actual, expected, pp) {
-    function handleAsymmetricExpected() {
-      if (
-        j$.isAsymmetricEqualityTester_(expected) &&
-        j$.isFunction_(expected.valuesForDiff_)
-      ) {
-        const asymmetricResult = expected.valuesForDiff_(actual, pp);
-        expected = asymmetricResult.self;
-        actual = asymmetricResult.other;
-      }
-    }
-
-    handleAsymmetricExpected();
-
-    for (const pc of objectPath.components) {
-      actual = actual[pc];
-      expected = expected[pc];
-      handleAsymmetricExpected();
-    }
-
-    return { actual: actual, expected: expected };
   }
+
+  function wrapPrettyPrinted(actual, expected, path) {
+    return (
+      'Expected ' +
+      path +
+      (path.depth() ? ' = ' : '') +
+      actual +
+      ' to equal ' +
+      expected +
+      '.'
+    );
+  }
+
+  return DiffBuilder;
 };
 
 getJasmineRequireObj().MatchersUtil = function(j$) {
@@ -5735,49 +5734,51 @@ getJasmineRequireObj().MismatchTree = function(j$) {
     the expected and actual object graphs. MismatchTree maintains that context
     and provides it via the traverse method.
    */
-  function MismatchTree(path) {
-    this.path = path || new j$.ObjectPath([]);
-    this.formatter = undefined;
-    this.children = [];
-    this.isMismatch = false;
-  }
-
-  MismatchTree.prototype.add = function(path, formatter) {
-    if (path.depth() === 0) {
-      this.formatter = formatter;
-      this.isMismatch = true;
-    } else {
-      const key = path.components[0];
-      path = path.shift();
-      let child = this.child(key);
-
-      if (!child) {
-        child = new MismatchTree(this.path.add(key));
-        this.children.push(child);
-      }
-
-      child.add(path, formatter);
+  class MismatchTree {
+    constructor(path) {
+      this.path = path || new j$.ObjectPath([]);
+      this.formatter = undefined;
+      this.children = [];
+      this.isMismatch = false;
     }
-  };
 
-  MismatchTree.prototype.traverse = function(visit) {
-    const hasChildren = this.children.length > 0;
+    add(path, formatter) {
+      if (path.depth() === 0) {
+        this.formatter = formatter;
+        this.isMismatch = true;
+      } else {
+        const key = path.components[0];
+        path = path.shift();
+        let child = this.child(key);
 
-    if (this.isMismatch || hasChildren) {
-      if (visit(this.path, !hasChildren, this.formatter)) {
-        for (const child of this.children) {
-          child.traverse(visit);
+        if (!child) {
+          child = new MismatchTree(this.path.add(key));
+          this.children.push(child);
+        }
+
+        child.add(path, formatter);
+      }
+    }
+
+    traverse(visit) {
+      const hasChildren = this.children.length > 0;
+
+      if (this.isMismatch || hasChildren) {
+        if (visit(this.path, !hasChildren, this.formatter)) {
+          for (const child of this.children) {
+            child.traverse(visit);
+          }
         }
       }
     }
-  };
 
-  MismatchTree.prototype.child = function(key) {
-    return this.children.find(child => {
-      const pathEls = child.path.components;
-      return pathEls[pathEls.length - 1] === key;
-    });
-  };
+    child(key) {
+      return this.children.find(child => {
+        const pathEls = child.path.components;
+        return pathEls[pathEls.length - 1] === key;
+      });
+    }
+  }
 
   return MismatchTree;
 };
@@ -5817,29 +5818,31 @@ getJasmineRequireObj().NullDiffBuilder = function(j$) {
 };
 
 getJasmineRequireObj().ObjectPath = function(j$) {
-  function ObjectPath(components) {
-    this.components = components || [];
-  }
-
-  ObjectPath.prototype.toString = function() {
-    if (this.components.length) {
-      return '$' + this.components.map(formatPropertyAccess).join('');
-    } else {
-      return '';
+  class ObjectPath {
+    constructor(components) {
+      this.components = components || [];
     }
-  };
 
-  ObjectPath.prototype.add = function(component) {
-    return new ObjectPath(this.components.concat([component]));
-  };
+    toString() {
+      if (this.components.length) {
+        return '$' + this.components.map(formatPropertyAccess).join('');
+      } else {
+        return '';
+      }
+    }
 
-  ObjectPath.prototype.shift = function() {
-    return new ObjectPath(this.components.slice(1));
-  };
+    add(component) {
+      return new ObjectPath(this.components.concat([component]));
+    }
 
-  ObjectPath.prototype.depth = function() {
-    return this.components.length;
-  };
+    shift() {
+      return new ObjectPath(this.components.slice(1));
+    }
+
+    depth() {
+      return this.components.length;
+    }
+  }
 
   function formatPropertyAccess(prop) {
     if (typeof prop === 'number' || typeof prop === 'symbol') {
@@ -5850,7 +5853,7 @@ getJasmineRequireObj().ObjectPath = function(j$) {
       return '.' + prop;
     }
 
-    return "['" + prop + "']";
+    return `['${prop}']`;
   }
 
   function isValidIdentifier(string) {
@@ -6415,7 +6418,7 @@ getJasmineRequireObj().toEqual = function(j$) {
         var result = {
             pass: false
           },
-          diffBuilder = j$.DiffBuilder({ prettyPrinter: matchersUtil.pp });
+          diffBuilder = new j$.DiffBuilder({ prettyPrinter: matchersUtil.pp });
 
         result.pass = matchersUtil.equals(actual, expected, diffBuilder);
 
@@ -7521,13 +7524,300 @@ getJasmineRequireObj().NeverSkipPolicy = function(j$) {
 };
 
 getJasmineRequireObj().makePrettyPrinter = function(j$) {
-  function SinglePrettyPrintRun(customObjectFormatters, pp) {
-    this.customObjectFormatters_ = customObjectFormatters;
-    this.ppNestLevel_ = 0;
-    this.seen = [];
-    this.length = 0;
-    this.stringParts = [];
-    this.pp_ = pp;
+  class SinglePrettyPrintRun {
+    constructor(customObjectFormatters, pp) {
+      this.customObjectFormatters_ = customObjectFormatters;
+      this.ppNestLevel_ = 0;
+      this.seen = [];
+      this.length = 0;
+      this.stringParts = [];
+      this.pp_ = pp;
+    }
+
+    format(value) {
+      this.ppNestLevel_++;
+      try {
+        const customFormatResult = this.applyCustomFormatters_(value);
+
+        if (customFormatResult) {
+          this.emitScalar(customFormatResult);
+        } else if (j$.util.isUndefined(value)) {
+          this.emitScalar('undefined');
+        } else if (value === null) {
+          this.emitScalar('null');
+        } else if (value === 0 && 1 / value === -Infinity) {
+          this.emitScalar('-0');
+        } else if (value === j$.getGlobal()) {
+          this.emitScalar('<global>');
+        } else if (value.jasmineToString) {
+          this.emitScalar(value.jasmineToString(this.pp_));
+        } else if (j$.isString_(value)) {
+          this.emitString(value);
+        } else if (j$.isSpy(value)) {
+          this.emitScalar('spy on ' + value.and.identity);
+        } else if (j$.isSpy(value.toString)) {
+          this.emitScalar('spy on ' + value.toString.and.identity);
+        } else if (value instanceof RegExp) {
+          this.emitScalar(value.toString());
+        } else if (typeof value === 'function') {
+          this.emitScalar('Function');
+        } else if (j$.isDomNode(value)) {
+          if (value.tagName) {
+            this.emitDomElement(value);
+          } else {
+            this.emitScalar('HTMLNode');
+          }
+        } else if (value instanceof Date) {
+          this.emitScalar('Date(' + value + ')');
+        } else if (j$.isSet(value)) {
+          this.emitSet(value);
+        } else if (j$.isMap(value)) {
+          this.emitMap(value);
+        } else if (j$.isTypedArray_(value)) {
+          this.emitTypedArray(value);
+        } else if (
+          value.toString &&
+          typeof value === 'object' &&
+          !j$.isArray_(value) &&
+          hasCustomToString(value)
+        ) {
+          try {
+            this.emitScalar(value.toString());
+          } catch (e) {
+            this.emitScalar('has-invalid-toString-method');
+          }
+        } else if (j$.util.arrayContains(this.seen, value)) {
+          this.emitScalar(
+            '<circular reference: ' +
+              (j$.isArray_(value) ? 'Array' : 'Object') +
+              '>'
+          );
+        } else if (j$.isArray_(value) || j$.isA_('Object', value)) {
+          this.seen.push(value);
+          if (j$.isArray_(value)) {
+            this.emitArray(value);
+          } else {
+            this.emitObject(value);
+          }
+          this.seen.pop();
+        } else {
+          this.emitScalar(value.toString());
+        }
+      } catch (e) {
+        if (this.ppNestLevel_ > 1 || !(e instanceof MaxCharsReachedError)) {
+          throw e;
+        }
+      } finally {
+        this.ppNestLevel_--;
+      }
+    }
+
+    applyCustomFormatters_(value) {
+      return customFormat(value, this.customObjectFormatters_);
+    }
+
+    iterateObject(obj, fn) {
+      const objKeys = j$.MatchersUtil.keys(obj, j$.isArray_(obj));
+      const length = Math.min(objKeys.length, j$.MAX_PRETTY_PRINT_ARRAY_LENGTH);
+
+      for (let i = 0; i < length; i++) {
+        fn(objKeys[i]);
+      }
+
+      return objKeys.length > length;
+    }
+
+    emitScalar(value) {
+      this.append(value);
+    }
+
+    emitString(value) {
+      this.append("'" + value + "'");
+    }
+
+    emitArray(array) {
+      if (this.ppNestLevel_ > j$.MAX_PRETTY_PRINT_DEPTH) {
+        this.append('Array');
+        return;
+      }
+
+      const length = Math.min(array.length, j$.MAX_PRETTY_PRINT_ARRAY_LENGTH);
+      this.append('[ ');
+
+      for (let i = 0; i < length; i++) {
+        if (i > 0) {
+          this.append(', ');
+        }
+        this.format(array[i]);
+      }
+      if (array.length > length) {
+        this.append(', ...');
+      }
+
+      let first = array.length === 0;
+      const wasTruncated = this.iterateObject(array, property => {
+        if (first) {
+          first = false;
+        } else {
+          this.append(', ');
+        }
+
+        this.formatProperty(array, property);
+      });
+
+      if (wasTruncated) {
+        this.append(', ...');
+      }
+
+      this.append(' ]');
+    }
+
+    emitSet(set) {
+      if (this.ppNestLevel_ > j$.MAX_PRETTY_PRINT_DEPTH) {
+        this.append('Set');
+        return;
+      }
+      this.append('Set( ');
+      const size = Math.min(set.size, j$.MAX_PRETTY_PRINT_ARRAY_LENGTH);
+      let i = 0;
+      set.forEach(function(value, key) {
+        if (i >= size) {
+          return;
+        }
+        if (i > 0) {
+          this.append(', ');
+        }
+        this.format(value);
+
+        i++;
+      }, this);
+      if (set.size > size) {
+        this.append(', ...');
+      }
+      this.append(' )');
+    }
+
+    emitMap(map) {
+      if (this.ppNestLevel_ > j$.MAX_PRETTY_PRINT_DEPTH) {
+        this.append('Map');
+        return;
+      }
+      this.append('Map( ');
+      const size = Math.min(map.size, j$.MAX_PRETTY_PRINT_ARRAY_LENGTH);
+      let i = 0;
+      map.forEach(function(value, key) {
+        if (i >= size) {
+          return;
+        }
+        if (i > 0) {
+          this.append(', ');
+        }
+        this.format([key, value]);
+
+        i++;
+      }, this);
+      if (map.size > size) {
+        this.append(', ...');
+      }
+      this.append(' )');
+    }
+
+    emitObject(obj) {
+      const ctor = obj.constructor;
+      const constructorName =
+        typeof ctor === 'function' && obj instanceof ctor
+          ? j$.fnNameFor(obj.constructor)
+          : 'null';
+
+      this.append(constructorName);
+
+      if (this.ppNestLevel_ > j$.MAX_PRETTY_PRINT_DEPTH) {
+        return;
+      }
+
+      this.append('({ ');
+      let first = true;
+
+      const wasTruncated = this.iterateObject(obj, property => {
+        if (first) {
+          first = false;
+        } else {
+          this.append(', ');
+        }
+
+        this.formatProperty(obj, property);
+      });
+
+      if (wasTruncated) {
+        this.append(', ...');
+      }
+
+      this.append(' })');
+    }
+
+    emitTypedArray(arr) {
+      const constructorName = j$.fnNameFor(arr.constructor);
+      const limitedArray = Array.prototype.slice.call(
+        arr,
+        0,
+        j$.MAX_PRETTY_PRINT_ARRAY_LENGTH
+      );
+      let itemsString = Array.prototype.join.call(limitedArray, ', ');
+
+      if (limitedArray.length !== arr.length) {
+        itemsString += ', ...';
+      }
+
+      this.append(constructorName + ' [ ' + itemsString + ' ]');
+    }
+
+    emitDomElement(el) {
+      const tagName = el.tagName.toLowerCase();
+      let out = '<' + tagName;
+
+      for (const attr of el.attributes) {
+        out += ' ' + attr.name;
+
+        if (attr.value !== '') {
+          out += '="' + attr.value + '"';
+        }
+      }
+
+      out += '>';
+
+      if (el.childElementCount !== 0 || el.textContent !== '') {
+        out += '...</' + tagName + '>';
+      }
+
+      this.append(out);
+    }
+
+    formatProperty(obj, property) {
+      if (typeof property === 'symbol') {
+        this.append(property.toString());
+      } else {
+        this.append(property);
+      }
+
+      this.append(': ');
+      this.format(obj[property]);
+    }
+
+    append(value) {
+      // This check protects us from the rare case where an object has overriden
+      // `toString()` with an invalid implementation (returning a non-string).
+      if (typeof value !== 'string') {
+        value = Object.prototype.toString.call(value);
+      }
+
+      const result = truncate(value, j$.MAX_PRETTY_PRINT_CHARS - this.length);
+      this.length += result.value.length;
+      this.stringParts.push(result.value);
+
+      if (result.truncated) {
+        throw new MaxCharsReachedError();
+      }
+    }
   }
 
   function hasCustomToString(value) {
@@ -7545,291 +7835,6 @@ getJasmineRequireObj().makePrettyPrinter = function(j$) {
     }
   }
 
-  SinglePrettyPrintRun.prototype.format = function(value) {
-    this.ppNestLevel_++;
-    try {
-      const customFormatResult = this.applyCustomFormatters_(value);
-
-      if (customFormatResult) {
-        this.emitScalar(customFormatResult);
-      } else if (j$.util.isUndefined(value)) {
-        this.emitScalar('undefined');
-      } else if (value === null) {
-        this.emitScalar('null');
-      } else if (value === 0 && 1 / value === -Infinity) {
-        this.emitScalar('-0');
-      } else if (value === j$.getGlobal()) {
-        this.emitScalar('<global>');
-      } else if (value.jasmineToString) {
-        this.emitScalar(value.jasmineToString(this.pp_));
-      } else if (j$.isString_(value)) {
-        this.emitString(value);
-      } else if (j$.isSpy(value)) {
-        this.emitScalar('spy on ' + value.and.identity);
-      } else if (j$.isSpy(value.toString)) {
-        this.emitScalar('spy on ' + value.toString.and.identity);
-      } else if (value instanceof RegExp) {
-        this.emitScalar(value.toString());
-      } else if (typeof value === 'function') {
-        this.emitScalar('Function');
-      } else if (j$.isDomNode(value)) {
-        if (value.tagName) {
-          this.emitDomElement(value);
-        } else {
-          this.emitScalar('HTMLNode');
-        }
-      } else if (value instanceof Date) {
-        this.emitScalar('Date(' + value + ')');
-      } else if (j$.isSet(value)) {
-        this.emitSet(value);
-      } else if (j$.isMap(value)) {
-        this.emitMap(value);
-      } else if (j$.isTypedArray_(value)) {
-        this.emitTypedArray(value);
-      } else if (
-        value.toString &&
-        typeof value === 'object' &&
-        !j$.isArray_(value) &&
-        hasCustomToString(value)
-      ) {
-        try {
-          this.emitScalar(value.toString());
-        } catch (e) {
-          this.emitScalar('has-invalid-toString-method');
-        }
-      } else if (j$.util.arrayContains(this.seen, value)) {
-        this.emitScalar(
-          '<circular reference: ' +
-            (j$.isArray_(value) ? 'Array' : 'Object') +
-            '>'
-        );
-      } else if (j$.isArray_(value) || j$.isA_('Object', value)) {
-        this.seen.push(value);
-        if (j$.isArray_(value)) {
-          this.emitArray(value);
-        } else {
-          this.emitObject(value);
-        }
-        this.seen.pop();
-      } else {
-        this.emitScalar(value.toString());
-      }
-    } catch (e) {
-      if (this.ppNestLevel_ > 1 || !(e instanceof MaxCharsReachedError)) {
-        throw e;
-      }
-    } finally {
-      this.ppNestLevel_--;
-    }
-  };
-
-  SinglePrettyPrintRun.prototype.applyCustomFormatters_ = function(value) {
-    return customFormat(value, this.customObjectFormatters_);
-  };
-
-  SinglePrettyPrintRun.prototype.iterateObject = function(obj, fn) {
-    const objKeys = j$.MatchersUtil.keys(obj, j$.isArray_(obj));
-    const length = Math.min(objKeys.length, j$.MAX_PRETTY_PRINT_ARRAY_LENGTH);
-
-    for (let i = 0; i < length; i++) {
-      fn(objKeys[i]);
-    }
-
-    return objKeys.length > length;
-  };
-
-  SinglePrettyPrintRun.prototype.emitScalar = function(value) {
-    this.append(value);
-  };
-
-  SinglePrettyPrintRun.prototype.emitString = function(value) {
-    this.append("'" + value + "'");
-  };
-
-  SinglePrettyPrintRun.prototype.emitArray = function(array) {
-    if (this.ppNestLevel_ > j$.MAX_PRETTY_PRINT_DEPTH) {
-      this.append('Array');
-      return;
-    }
-
-    const length = Math.min(array.length, j$.MAX_PRETTY_PRINT_ARRAY_LENGTH);
-    this.append('[ ');
-
-    for (let i = 0; i < length; i++) {
-      if (i > 0) {
-        this.append(', ');
-      }
-      this.format(array[i]);
-    }
-    if (array.length > length) {
-      this.append(', ...');
-    }
-
-    let first = array.length === 0;
-    const wasTruncated = this.iterateObject(array, property => {
-      if (first) {
-        first = false;
-      } else {
-        this.append(', ');
-      }
-
-      this.formatProperty(array, property);
-    });
-
-    if (wasTruncated) {
-      this.append(', ...');
-    }
-
-    this.append(' ]');
-  };
-
-  SinglePrettyPrintRun.prototype.emitSet = function(set) {
-    if (this.ppNestLevel_ > j$.MAX_PRETTY_PRINT_DEPTH) {
-      this.append('Set');
-      return;
-    }
-    this.append('Set( ');
-    const size = Math.min(set.size, j$.MAX_PRETTY_PRINT_ARRAY_LENGTH);
-    let i = 0;
-    set.forEach(function(value, key) {
-      if (i >= size) {
-        return;
-      }
-      if (i > 0) {
-        this.append(', ');
-      }
-      this.format(value);
-
-      i++;
-    }, this);
-    if (set.size > size) {
-      this.append(', ...');
-    }
-    this.append(' )');
-  };
-
-  SinglePrettyPrintRun.prototype.emitMap = function(map) {
-    if (this.ppNestLevel_ > j$.MAX_PRETTY_PRINT_DEPTH) {
-      this.append('Map');
-      return;
-    }
-    this.append('Map( ');
-    const size = Math.min(map.size, j$.MAX_PRETTY_PRINT_ARRAY_LENGTH);
-    let i = 0;
-    map.forEach(function(value, key) {
-      if (i >= size) {
-        return;
-      }
-      if (i > 0) {
-        this.append(', ');
-      }
-      this.format([key, value]);
-
-      i++;
-    }, this);
-    if (map.size > size) {
-      this.append(', ...');
-    }
-    this.append(' )');
-  };
-
-  SinglePrettyPrintRun.prototype.emitObject = function(obj) {
-    const ctor = obj.constructor;
-    const constructorName =
-      typeof ctor === 'function' && obj instanceof ctor
-        ? j$.fnNameFor(obj.constructor)
-        : 'null';
-
-    this.append(constructorName);
-
-    if (this.ppNestLevel_ > j$.MAX_PRETTY_PRINT_DEPTH) {
-      return;
-    }
-
-    this.append('({ ');
-    let first = true;
-
-    const wasTruncated = this.iterateObject(obj, property => {
-      if (first) {
-        first = false;
-      } else {
-        this.append(', ');
-      }
-
-      this.formatProperty(obj, property);
-    });
-
-    if (wasTruncated) {
-      this.append(', ...');
-    }
-
-    this.append(' })');
-  };
-
-  SinglePrettyPrintRun.prototype.emitTypedArray = function(arr) {
-    const constructorName = j$.fnNameFor(arr.constructor);
-    const limitedArray = Array.prototype.slice.call(
-      arr,
-      0,
-      j$.MAX_PRETTY_PRINT_ARRAY_LENGTH
-    );
-    let itemsString = Array.prototype.join.call(limitedArray, ', ');
-
-    if (limitedArray.length !== arr.length) {
-      itemsString += ', ...';
-    }
-
-    this.append(constructorName + ' [ ' + itemsString + ' ]');
-  };
-
-  SinglePrettyPrintRun.prototype.emitDomElement = function(el) {
-    const tagName = el.tagName.toLowerCase();
-    let out = '<' + tagName;
-
-    for (const attr of el.attributes) {
-      out += ' ' + attr.name;
-
-      if (attr.value !== '') {
-        out += '="' + attr.value + '"';
-      }
-    }
-
-    out += '>';
-
-    if (el.childElementCount !== 0 || el.textContent !== '') {
-      out += '...</' + tagName + '>';
-    }
-
-    this.append(out);
-  };
-
-  SinglePrettyPrintRun.prototype.formatProperty = function(obj, property) {
-    if (typeof property === 'symbol') {
-      this.append(property.toString());
-    } else {
-      this.append(property);
-    }
-
-    this.append(': ');
-    this.format(obj[property]);
-  };
-
-  SinglePrettyPrintRun.prototype.append = function(value) {
-    // This check protects us from the rare case where an object has overriden
-    // `toString()` with an invalid implementation (returning a non-string).
-    if (typeof value !== 'string') {
-      value = Object.prototype.toString.call(value);
-    }
-
-    const result = truncate(value, j$.MAX_PRETTY_PRINT_CHARS - this.length);
-    this.length += result.value.length;
-    this.stringParts.push(result.value);
-
-    if (result.truncated) {
-      throw new MaxCharsReachedError();
-    }
-  };
-
   function truncate(s, maxlen) {
     if (s.length <= maxlen) {
       return { value: s, truncated: false };
diff --git a/spec/core/matchers/DiffBuilderSpec.js b/spec/core/matchers/DiffBuilderSpec.js
index 69753bf5..b15d0e2c 100644
--- a/spec/core/matchers/DiffBuilderSpec.js
+++ b/spec/core/matchers/DiffBuilderSpec.js
@@ -1,6 +1,6 @@
 describe('DiffBuilder', function() {
   it('records the actual and expected objects', function() {
-    const diffBuilder = jasmineUnderTest.DiffBuilder();
+    const diffBuilder = new jasmineUnderTest.DiffBuilder();
     diffBuilder.setRoots({ x: 'actual' }, { x: 'expected' });
     diffBuilder.recordMismatch();
 
@@ -10,7 +10,7 @@ describe('DiffBuilder', function() {
   });
 
   it('prints the path at which the difference was found', function() {
-    const diffBuilder = jasmineUnderTest.DiffBuilder();
+    const diffBuilder = new jasmineUnderTest.DiffBuilder();
     diffBuilder.setRoots({ foo: { x: 'actual' } }, { foo: { x: 'expected' } });
 
     diffBuilder.withPath('foo', function() {
@@ -23,7 +23,7 @@ describe('DiffBuilder', function() {
   });
 
   it('prints multiple messages, separated by newlines', function() {
-    const diffBuilder = jasmineUnderTest.DiffBuilder();
+    const diffBuilder = new jasmineUnderTest.DiffBuilder();
     diffBuilder.setRoots({ foo: 1, bar: 3 }, { foo: 2, bar: 4 });
 
     diffBuilder.withPath('foo', function() {
@@ -40,7 +40,7 @@ describe('DiffBuilder', function() {
   });
 
   it('allows customization of the message', function() {
-    const diffBuilder = jasmineUnderTest.DiffBuilder();
+    const diffBuilder = new jasmineUnderTest.DiffBuilder();
     diffBuilder.setRoots({ x: 'bar' }, { x: 'foo' });
 
     function darthVaderFormatter(actual, expected, path) {
@@ -68,7 +68,7 @@ describe('DiffBuilder', function() {
     const prettyPrinter = function(val) {
         return '|' + val + '|';
       },
-      diffBuilder = jasmineUnderTest.DiffBuilder({
+      diffBuilder = new jasmineUnderTest.DiffBuilder({
         prettyPrinter: prettyPrinter
       });
     prettyPrinter.customFormat_ = function() {};
@@ -86,7 +86,7 @@ describe('DiffBuilder', function() {
   it('passes the injected pretty-printer to the diff formatter', function() {
     const diffFormatter = jasmine.createSpy('diffFormatter'),
       prettyPrinter = function() {},
-      diffBuilder = jasmineUnderTest.DiffBuilder({
+      diffBuilder = new jasmineUnderTest.DiffBuilder({
         prettyPrinter: prettyPrinter
       });
     prettyPrinter.customFormat_ = function() {};
diff --git a/src/core/PrettyPrinter.js b/src/core/PrettyPrinter.js
index 8e1dae36..f3231359 100644
--- a/src/core/PrettyPrinter.js
+++ b/src/core/PrettyPrinter.js
@@ -1,11 +1,298 @@
 getJasmineRequireObj().makePrettyPrinter = function(j$) {
-  function SinglePrettyPrintRun(customObjectFormatters, pp) {
-    this.customObjectFormatters_ = customObjectFormatters;
-    this.ppNestLevel_ = 0;
-    this.seen = [];
-    this.length = 0;
-    this.stringParts = [];
-    this.pp_ = pp;
+  class SinglePrettyPrintRun {
+    constructor(customObjectFormatters, pp) {
+      this.customObjectFormatters_ = customObjectFormatters;
+      this.ppNestLevel_ = 0;
+      this.seen = [];
+      this.length = 0;
+      this.stringParts = [];
+      this.pp_ = pp;
+    }
+
+    format(value) {
+      this.ppNestLevel_++;
+      try {
+        const customFormatResult = this.applyCustomFormatters_(value);
+
+        if (customFormatResult) {
+          this.emitScalar(customFormatResult);
+        } else if (j$.util.isUndefined(value)) {
+          this.emitScalar('undefined');
+        } else if (value === null) {
+          this.emitScalar('null');
+        } else if (value === 0 && 1 / value === -Infinity) {
+          this.emitScalar('-0');
+        } else if (value === j$.getGlobal()) {
+          this.emitScalar('<global>');
+        } else if (value.jasmineToString) {
+          this.emitScalar(value.jasmineToString(this.pp_));
+        } else if (j$.isString_(value)) {
+          this.emitString(value);
+        } else if (j$.isSpy(value)) {
+          this.emitScalar('spy on ' + value.and.identity);
+        } else if (j$.isSpy(value.toString)) {
+          this.emitScalar('spy on ' + value.toString.and.identity);
+        } else if (value instanceof RegExp) {
+          this.emitScalar(value.toString());
+        } else if (typeof value === 'function') {
+          this.emitScalar('Function');
+        } else if (j$.isDomNode(value)) {
+          if (value.tagName) {
+            this.emitDomElement(value);
+          } else {
+            this.emitScalar('HTMLNode');
+          }
+        } else if (value instanceof Date) {
+          this.emitScalar('Date(' + value + ')');
+        } else if (j$.isSet(value)) {
+          this.emitSet(value);
+        } else if (j$.isMap(value)) {
+          this.emitMap(value);
+        } else if (j$.isTypedArray_(value)) {
+          this.emitTypedArray(value);
+        } else if (
+          value.toString &&
+          typeof value === 'object' &&
+          !j$.isArray_(value) &&
+          hasCustomToString(value)
+        ) {
+          try {
+            this.emitScalar(value.toString());
+          } catch (e) {
+            this.emitScalar('has-invalid-toString-method');
+          }
+        } else if (j$.util.arrayContains(this.seen, value)) {
+          this.emitScalar(
+            '<circular reference: ' +
+              (j$.isArray_(value) ? 'Array' : 'Object') +
+              '>'
+          );
+        } else if (j$.isArray_(value) || j$.isA_('Object', value)) {
+          this.seen.push(value);
+          if (j$.isArray_(value)) {
+            this.emitArray(value);
+          } else {
+            this.emitObject(value);
+          }
+          this.seen.pop();
+        } else {
+          this.emitScalar(value.toString());
+        }
+      } catch (e) {
+        if (this.ppNestLevel_ > 1 || !(e instanceof MaxCharsReachedError)) {
+          throw e;
+        }
+      } finally {
+        this.ppNestLevel_--;
+      }
+    }
+
+    applyCustomFormatters_(value) {
+      return customFormat(value, this.customObjectFormatters_);
+    }
+
+    iterateObject(obj, fn) {
+      const objKeys = j$.MatchersUtil.keys(obj, j$.isArray_(obj));
+      const length = Math.min(objKeys.length, j$.MAX_PRETTY_PRINT_ARRAY_LENGTH);
+
+      for (let i = 0; i < length; i++) {
+        fn(objKeys[i]);
+      }
+
+      return objKeys.length > length;
+    }
+
+    emitScalar(value) {
+      this.append(value);
+    }
+
+    emitString(value) {
+      this.append("'" + value + "'");
+    }
+
+    emitArray(array) {
+      if (this.ppNestLevel_ > j$.MAX_PRETTY_PRINT_DEPTH) {
+        this.append('Array');
+        return;
+      }
+
+      const length = Math.min(array.length, j$.MAX_PRETTY_PRINT_ARRAY_LENGTH);
+      this.append('[ ');
+
+      for (let i = 0; i < length; i++) {
+        if (i > 0) {
+          this.append(', ');
+        }
+        this.format(array[i]);
+      }
+      if (array.length > length) {
+        this.append(', ...');
+      }
+
+      let first = array.length === 0;
+      const wasTruncated = this.iterateObject(array, property => {
+        if (first) {
+          first = false;
+        } else {
+          this.append(', ');
+        }
+
+        this.formatProperty(array, property);
+      });
+
+      if (wasTruncated) {
+        this.append(', ...');
+      }
+
+      this.append(' ]');
+    }
+
+    emitSet(set) {
+      if (this.ppNestLevel_ > j$.MAX_PRETTY_PRINT_DEPTH) {
+        this.append('Set');
+        return;
+      }
+      this.append('Set( ');
+      const size = Math.min(set.size, j$.MAX_PRETTY_PRINT_ARRAY_LENGTH);
+      let i = 0;
+      set.forEach(function(value, key) {
+        if (i >= size) {
+          return;
+        }
+        if (i > 0) {
+          this.append(', ');
+        }
+        this.format(value);
+
+        i++;
+      }, this);
+      if (set.size > size) {
+        this.append(', ...');
+      }
+      this.append(' )');
+    }
+
+    emitMap(map) {
+      if (this.ppNestLevel_ > j$.MAX_PRETTY_PRINT_DEPTH) {
+        this.append('Map');
+        return;
+      }
+      this.append('Map( ');
+      const size = Math.min(map.size, j$.MAX_PRETTY_PRINT_ARRAY_LENGTH);
+      let i = 0;
+      map.forEach(function(value, key) {
+        if (i >= size) {
+          return;
+        }
+        if (i > 0) {
+          this.append(', ');
+        }
+        this.format([key, value]);
+
+        i++;
+      }, this);
+      if (map.size > size) {
+        this.append(', ...');
+      }
+      this.append(' )');
+    }
+
+    emitObject(obj) {
+      const ctor = obj.constructor;
+      const constructorName =
+        typeof ctor === 'function' && obj instanceof ctor
+          ? j$.fnNameFor(obj.constructor)
+          : 'null';
+
+      this.append(constructorName);
+
+      if (this.ppNestLevel_ > j$.MAX_PRETTY_PRINT_DEPTH) {
+        return;
+      }
+
+      this.append('({ ');
+      let first = true;
+
+      const wasTruncated = this.iterateObject(obj, property => {
+        if (first) {
+          first = false;
+        } else {
+          this.append(', ');
+        }
+
+        this.formatProperty(obj, property);
+      });
+
+      if (wasTruncated) {
+        this.append(', ...');
+      }
+
+      this.append(' })');
+    }
+
+    emitTypedArray(arr) {
+      const constructorName = j$.fnNameFor(arr.constructor);
+      const limitedArray = Array.prototype.slice.call(
+        arr,
+        0,
+        j$.MAX_PRETTY_PRINT_ARRAY_LENGTH
+      );
+      let itemsString = Array.prototype.join.call(limitedArray, ', ');
+
+      if (limitedArray.length !== arr.length) {
+        itemsString += ', ...';
+      }
+
+      this.append(constructorName + ' [ ' + itemsString + ' ]');
+    }
+
+    emitDomElement(el) {
+      const tagName = el.tagName.toLowerCase();
+      let out = '<' + tagName;
+
+      for (const attr of el.attributes) {
+        out += ' ' + attr.name;
+
+        if (attr.value !== '') {
+          out += '="' + attr.value + '"';
+        }
+      }
+
+      out += '>';
+
+      if (el.childElementCount !== 0 || el.textContent !== '') {
+        out += '...</' + tagName + '>';
+      }
+
+      this.append(out);
+    }
+
+    formatProperty(obj, property) {
+      if (typeof property === 'symbol') {
+        this.append(property.toString());
+      } else {
+        this.append(property);
+      }
+
+      this.append(': ');
+      this.format(obj[property]);
+    }
+
+    append(value) {
+      // This check protects us from the rare case where an object has overriden
+      // `toString()` with an invalid implementation (returning a non-string).
+      if (typeof value !== 'string') {
+        value = Object.prototype.toString.call(value);
+      }
+
+      const result = truncate(value, j$.MAX_PRETTY_PRINT_CHARS - this.length);
+      this.length += result.value.length;
+      this.stringParts.push(result.value);
+
+      if (result.truncated) {
+        throw new MaxCharsReachedError();
+      }
+    }
   }
 
   function hasCustomToString(value) {
@@ -23,291 +310,6 @@ getJasmineRequireObj().makePrettyPrinter = function(j$) {
     }
   }
 
-  SinglePrettyPrintRun.prototype.format = function(value) {
-    this.ppNestLevel_++;
-    try {
-      const customFormatResult = this.applyCustomFormatters_(value);
-
-      if (customFormatResult) {
-        this.emitScalar(customFormatResult);
-      } else if (j$.util.isUndefined(value)) {
-        this.emitScalar('undefined');
-      } else if (value === null) {
-        this.emitScalar('null');
-      } else if (value === 0 && 1 / value === -Infinity) {
-        this.emitScalar('-0');
-      } else if (value === j$.getGlobal()) {
-        this.emitScalar('<global>');
-      } else if (value.jasmineToString) {
-        this.emitScalar(value.jasmineToString(this.pp_));
-      } else if (j$.isString_(value)) {
-        this.emitString(value);
-      } else if (j$.isSpy(value)) {
-        this.emitScalar('spy on ' + value.and.identity);
-      } else if (j$.isSpy(value.toString)) {
-        this.emitScalar('spy on ' + value.toString.and.identity);
-      } else if (value instanceof RegExp) {
-        this.emitScalar(value.toString());
-      } else if (typeof value === 'function') {
-        this.emitScalar('Function');
-      } else if (j$.isDomNode(value)) {
-        if (value.tagName) {
-          this.emitDomElement(value);
-        } else {
-          this.emitScalar('HTMLNode');
-        }
-      } else if (value instanceof Date) {
-        this.emitScalar('Date(' + value + ')');
-      } else if (j$.isSet(value)) {
-        this.emitSet(value);
-      } else if (j$.isMap(value)) {
-        this.emitMap(value);
-      } else if (j$.isTypedArray_(value)) {
-        this.emitTypedArray(value);
-      } else if (
-        value.toString &&
-        typeof value === 'object' &&
-        !j$.isArray_(value) &&
-        hasCustomToString(value)
-      ) {
-        try {
-          this.emitScalar(value.toString());
-        } catch (e) {
-          this.emitScalar('has-invalid-toString-method');
-        }
-      } else if (j$.util.arrayContains(this.seen, value)) {
-        this.emitScalar(
-          '<circular reference: ' +
-            (j$.isArray_(value) ? 'Array' : 'Object') +
-            '>'
-        );
-      } else if (j$.isArray_(value) || j$.isA_('Object', value)) {
-        this.seen.push(value);
-        if (j$.isArray_(value)) {
-          this.emitArray(value);
-        } else {
-          this.emitObject(value);
-        }
-        this.seen.pop();
-      } else {
-        this.emitScalar(value.toString());
-      }
-    } catch (e) {
-      if (this.ppNestLevel_ > 1 || !(e instanceof MaxCharsReachedError)) {
-        throw e;
-      }
-    } finally {
-      this.ppNestLevel_--;
-    }
-  };
-
-  SinglePrettyPrintRun.prototype.applyCustomFormatters_ = function(value) {
-    return customFormat(value, this.customObjectFormatters_);
-  };
-
-  SinglePrettyPrintRun.prototype.iterateObject = function(obj, fn) {
-    const objKeys = j$.MatchersUtil.keys(obj, j$.isArray_(obj));
-    const length = Math.min(objKeys.length, j$.MAX_PRETTY_PRINT_ARRAY_LENGTH);
-
-    for (let i = 0; i < length; i++) {
-      fn(objKeys[i]);
-    }
-
-    return objKeys.length > length;
-  };
-
-  SinglePrettyPrintRun.prototype.emitScalar = function(value) {
-    this.append(value);
-  };
-
-  SinglePrettyPrintRun.prototype.emitString = function(value) {
-    this.append("'" + value + "'");
-  };
-
-  SinglePrettyPrintRun.prototype.emitArray = function(array) {
-    if (this.ppNestLevel_ > j$.MAX_PRETTY_PRINT_DEPTH) {
-      this.append('Array');
-      return;
-    }
-
-    const length = Math.min(array.length, j$.MAX_PRETTY_PRINT_ARRAY_LENGTH);
-    this.append('[ ');
-
-    for (let i = 0; i < length; i++) {
-      if (i > 0) {
-        this.append(', ');
-      }
-      this.format(array[i]);
-    }
-    if (array.length > length) {
-      this.append(', ...');
-    }
-
-    let first = array.length === 0;
-    const wasTruncated = this.iterateObject(array, property => {
-      if (first) {
-        first = false;
-      } else {
-        this.append(', ');
-      }
-
-      this.formatProperty(array, property);
-    });
-
-    if (wasTruncated) {
-      this.append(', ...');
-    }
-
-    this.append(' ]');
-  };
-
-  SinglePrettyPrintRun.prototype.emitSet = function(set) {
-    if (this.ppNestLevel_ > j$.MAX_PRETTY_PRINT_DEPTH) {
-      this.append('Set');
-      return;
-    }
-    this.append('Set( ');
-    const size = Math.min(set.size, j$.MAX_PRETTY_PRINT_ARRAY_LENGTH);
-    let i = 0;
-    set.forEach(function(value, key) {
-      if (i >= size) {
-        return;
-      }
-      if (i > 0) {
-        this.append(', ');
-      }
-      this.format(value);
-
-      i++;
-    }, this);
-    if (set.size > size) {
-      this.append(', ...');
-    }
-    this.append(' )');
-  };
-
-  SinglePrettyPrintRun.prototype.emitMap = function(map) {
-    if (this.ppNestLevel_ > j$.MAX_PRETTY_PRINT_DEPTH) {
-      this.append('Map');
-      return;
-    }
-    this.append('Map( ');
-    const size = Math.min(map.size, j$.MAX_PRETTY_PRINT_ARRAY_LENGTH);
-    let i = 0;
-    map.forEach(function(value, key) {
-      if (i >= size) {
-        return;
-      }
-      if (i > 0) {
-        this.append(', ');
-      }
-      this.format([key, value]);
-
-      i++;
-    }, this);
-    if (map.size > size) {
-      this.append(', ...');
-    }
-    this.append(' )');
-  };
-
-  SinglePrettyPrintRun.prototype.emitObject = function(obj) {
-    const ctor = obj.constructor;
-    const constructorName =
-      typeof ctor === 'function' && obj instanceof ctor
-        ? j$.fnNameFor(obj.constructor)
-        : 'null';
-
-    this.append(constructorName);
-
-    if (this.ppNestLevel_ > j$.MAX_PRETTY_PRINT_DEPTH) {
-      return;
-    }
-
-    this.append('({ ');
-    let first = true;
-
-    const wasTruncated = this.iterateObject(obj, property => {
-      if (first) {
-        first = false;
-      } else {
-        this.append(', ');
-      }
-
-      this.formatProperty(obj, property);
-    });
-
-    if (wasTruncated) {
-      this.append(', ...');
-    }
-
-    this.append(' })');
-  };
-
-  SinglePrettyPrintRun.prototype.emitTypedArray = function(arr) {
-    const constructorName = j$.fnNameFor(arr.constructor);
-    const limitedArray = Array.prototype.slice.call(
-      arr,
-      0,
-      j$.MAX_PRETTY_PRINT_ARRAY_LENGTH
-    );
-    let itemsString = Array.prototype.join.call(limitedArray, ', ');
-
-    if (limitedArray.length !== arr.length) {
-      itemsString += ', ...';
-    }
-
-    this.append(constructorName + ' [ ' + itemsString + ' ]');
-  };
-
-  SinglePrettyPrintRun.prototype.emitDomElement = function(el) {
-    const tagName = el.tagName.toLowerCase();
-    let out = '<' + tagName;
-
-    for (const attr of el.attributes) {
-      out += ' ' + attr.name;
-
-      if (attr.value !== '') {
-        out += '="' + attr.value + '"';
-      }
-    }
-
-    out += '>';
-
-    if (el.childElementCount !== 0 || el.textContent !== '') {
-      out += '...</' + tagName + '>';
-    }
-
-    this.append(out);
-  };
-
-  SinglePrettyPrintRun.prototype.formatProperty = function(obj, property) {
-    if (typeof property === 'symbol') {
-      this.append(property.toString());
-    } else {
-      this.append(property);
-    }
-
-    this.append(': ');
-    this.format(obj[property]);
-  };
-
-  SinglePrettyPrintRun.prototype.append = function(value) {
-    // This check protects us from the rare case where an object has overriden
-    // `toString()` with an invalid implementation (returning a non-string).
-    if (typeof value !== 'string') {
-      value = Object.prototype.toString.call(value);
-    }
-
-    const result = truncate(value, j$.MAX_PRETTY_PRINT_CHARS - this.length);
-    this.length += result.value.length;
-    this.stringParts.push(result.value);
-
-    if (result.truncated) {
-      throw new MaxCharsReachedError();
-    }
-  };
-
   function truncate(s, maxlen) {
     if (s.length <= maxlen) {
       return { value: s, truncated: false };
diff --git a/src/core/matchers/DiffBuilder.js b/src/core/matchers/DiffBuilder.js
index 50da9a69..8a6da6a4 100644
--- a/src/core/matchers/DiffBuilder.js
+++ b/src/core/matchers/DiffBuilder.js
@@ -1,113 +1,112 @@
 getJasmineRequireObj().DiffBuilder = function(j$) {
-  return function DiffBuilder(config) {
-    const prettyPrinter =
-      (config || {}).prettyPrinter || j$.makePrettyPrinter();
-    const mismatches = new j$.MismatchTree();
-    let path = new j$.ObjectPath();
-    let actualRoot = undefined;
-    let expectedRoot = undefined;
+  class DiffBuilder {
+    constructor(config) {
+      this.prettyPrinter_ =
+        (config || {}).prettyPrinter || j$.makePrettyPrinter();
+      this.mismatches_ = new j$.MismatchTree();
+      this.path_ = new j$.ObjectPath();
+      this.actualRoot_ = undefined;
+      this.expectedRoot_ = undefined;
+    }
 
-    return {
-      setRoots: function(actual, expected) {
-        actualRoot = actual;
-        expectedRoot = expected;
-      },
+    setRoots(actual, expected) {
+      this.actualRoot_ = actual;
+      this.expectedRoot_ = expected;
+    }
 
-      recordMismatch: function(formatter) {
-        mismatches.add(path, formatter);
-      },
+    recordMismatch(formatter) {
+      this.mismatches_.add(this.path_, formatter);
+    }
 
-      getMessage: function() {
-        const messages = [];
+    getMessage() {
+      const messages = [];
 
-        mismatches.traverse(function(path, isLeaf, formatter) {
-          const { actual, expected } = dereferencePath(
-            path,
-            actualRoot,
-            expectedRoot,
-            prettyPrinter
-          );
-
-          if (formatter) {
-            messages.push(formatter(actual, expected, path, prettyPrinter));
-            return true;
-          }
-
-          const actualCustom = prettyPrinter.customFormat_(actual);
-          const expectedCustom = prettyPrinter.customFormat_(expected);
-          const useCustom = !(
-            j$.util.isUndefined(actualCustom) &&
-            j$.util.isUndefined(expectedCustom)
-          );
-
-          if (useCustom) {
-            messages.push(
-              wrapPrettyPrinted(actualCustom, expectedCustom, path)
-            );
-            return false; // don't recurse further
-          }
-
-          if (isLeaf) {
-            messages.push(
-              defaultFormatter(actual, expected, path, prettyPrinter)
-            );
-          }
+      this.mismatches_.traverse((path, isLeaf, formatter) => {
+        const { actual, expected } = this.dereferencePath_(path);
 
+        if (formatter) {
+          messages.push(formatter(actual, expected, path, this.prettyPrinter_));
           return true;
-        });
+        }
 
-        return messages.join('\n');
-      },
+        const actualCustom = this.prettyPrinter_.customFormat_(actual);
+        const expectedCustom = this.prettyPrinter_.customFormat_(expected);
+        const useCustom = !(
+          j$.util.isUndefined(actualCustom) &&
+          j$.util.isUndefined(expectedCustom)
+        );
 
-      withPath: function(pathComponent, block) {
-        const oldPath = path;
-        path = path.add(pathComponent);
-        block();
-        path = oldPath;
+        if (useCustom) {
+          messages.push(wrapPrettyPrinted(actualCustom, expectedCustom, path));
+          return false; // don't recurse further
+        }
+
+        if (isLeaf) {
+          messages.push(this.defaultFormatter_(actual, expected, path));
+        }
+
+        return true;
+      });
+
+      return messages.join('\n');
+    }
+
+    withPath(pathComponent, block) {
+      const oldPath = this.path_;
+      this.path_ = this.path_.add(pathComponent);
+      block();
+      this.path_ = oldPath;
+    }
+
+    dereferencePath_(objectPath) {
+      let actual = this.actualRoot_;
+      let expected = this.expectedRoot_;
+
+      const handleAsymmetricExpected = () => {
+        if (
+          j$.isAsymmetricEqualityTester_(expected) &&
+          j$.isFunction_(expected.valuesForDiff_)
+        ) {
+          const asymmetricResult = expected.valuesForDiff_(
+            actual,
+            this.prettyPrinter_
+          );
+          expected = asymmetricResult.self;
+          actual = asymmetricResult.other;
+        }
+      };
+
+      handleAsymmetricExpected();
+
+      for (const pc of objectPath.components) {
+        actual = actual[pc];
+        expected = expected[pc];
+        handleAsymmetricExpected();
       }
-    };
 
-    function defaultFormatter(actual, expected, path, prettyPrinter) {
+      return { actual: actual, expected: expected };
+    }
+
+    defaultFormatter_(actual, expected, path) {
       return wrapPrettyPrinted(
-        prettyPrinter(actual),
-        prettyPrinter(expected),
+        this.prettyPrinter_(actual),
+        this.prettyPrinter_(expected),
         path
       );
     }
-
-    function wrapPrettyPrinted(actual, expected, path) {
-      return (
-        'Expected ' +
-        path +
-        (path.depth() ? ' = ' : '') +
-        actual +
-        ' to equal ' +
-        expected +
-        '.'
-      );
-    }
-  };
-
-  function dereferencePath(objectPath, actual, expected, pp) {
-    function handleAsymmetricExpected() {
-      if (
-        j$.isAsymmetricEqualityTester_(expected) &&
-        j$.isFunction_(expected.valuesForDiff_)
-      ) {
-        const asymmetricResult = expected.valuesForDiff_(actual, pp);
-        expected = asymmetricResult.self;
-        actual = asymmetricResult.other;
-      }
-    }
-
-    handleAsymmetricExpected();
-
-    for (const pc of objectPath.components) {
-      actual = actual[pc];
-      expected = expected[pc];
-      handleAsymmetricExpected();
-    }
-
-    return { actual: actual, expected: expected };
   }
+
+  function wrapPrettyPrinted(actual, expected, path) {
+    return (
+      'Expected ' +
+      path +
+      (path.depth() ? ' = ' : '') +
+      actual +
+      ' to equal ' +
+      expected +
+      '.'
+    );
+  }
+
+  return DiffBuilder;
 };
diff --git a/src/core/matchers/MismatchTree.js b/src/core/matchers/MismatchTree.js
index 9836b2d9..85176563 100644
--- a/src/core/matchers/MismatchTree.js
+++ b/src/core/matchers/MismatchTree.js
@@ -6,49 +6,51 @@ getJasmineRequireObj().MismatchTree = function(j$) {
     the expected and actual object graphs. MismatchTree maintains that context
     and provides it via the traverse method.
    */
-  function MismatchTree(path) {
-    this.path = path || new j$.ObjectPath([]);
-    this.formatter = undefined;
-    this.children = [];
-    this.isMismatch = false;
-  }
-
-  MismatchTree.prototype.add = function(path, formatter) {
-    if (path.depth() === 0) {
-      this.formatter = formatter;
-      this.isMismatch = true;
-    } else {
-      const key = path.components[0];
-      path = path.shift();
-      let child = this.child(key);
-
-      if (!child) {
-        child = new MismatchTree(this.path.add(key));
-        this.children.push(child);
-      }
-
-      child.add(path, formatter);
+  class MismatchTree {
+    constructor(path) {
+      this.path = path || new j$.ObjectPath([]);
+      this.formatter = undefined;
+      this.children = [];
+      this.isMismatch = false;
     }
-  };
 
-  MismatchTree.prototype.traverse = function(visit) {
-    const hasChildren = this.children.length > 0;
+    add(path, formatter) {
+      if (path.depth() === 0) {
+        this.formatter = formatter;
+        this.isMismatch = true;
+      } else {
+        const key = path.components[0];
+        path = path.shift();
+        let child = this.child(key);
 
-    if (this.isMismatch || hasChildren) {
-      if (visit(this.path, !hasChildren, this.formatter)) {
-        for (const child of this.children) {
-          child.traverse(visit);
+        if (!child) {
+          child = new MismatchTree(this.path.add(key));
+          this.children.push(child);
+        }
+
+        child.add(path, formatter);
+      }
+    }
+
+    traverse(visit) {
+      const hasChildren = this.children.length > 0;
+
+      if (this.isMismatch || hasChildren) {
+        if (visit(this.path, !hasChildren, this.formatter)) {
+          for (const child of this.children) {
+            child.traverse(visit);
+          }
         }
       }
     }
-  };
 
-  MismatchTree.prototype.child = function(key) {
-    return this.children.find(child => {
-      const pathEls = child.path.components;
-      return pathEls[pathEls.length - 1] === key;
-    });
-  };
+    child(key) {
+      return this.children.find(child => {
+        const pathEls = child.path.components;
+        return pathEls[pathEls.length - 1] === key;
+      });
+    }
+  }
 
   return MismatchTree;
 };
diff --git a/src/core/matchers/ObjectPath.js b/src/core/matchers/ObjectPath.js
index f4225d5c..e87e17de 100644
--- a/src/core/matchers/ObjectPath.js
+++ b/src/core/matchers/ObjectPath.js
@@ -1,27 +1,29 @@
 getJasmineRequireObj().ObjectPath = function(j$) {
-  function ObjectPath(components) {
-    this.components = components || [];
-  }
-
-  ObjectPath.prototype.toString = function() {
-    if (this.components.length) {
-      return '$' + this.components.map(formatPropertyAccess).join('');
-    } else {
-      return '';
+  class ObjectPath {
+    constructor(components) {
+      this.components = components || [];
     }
-  };
 
-  ObjectPath.prototype.add = function(component) {
-    return new ObjectPath(this.components.concat([component]));
-  };
+    toString() {
+      if (this.components.length) {
+        return '$' + this.components.map(formatPropertyAccess).join('');
+      } else {
+        return '';
+      }
+    }
 
-  ObjectPath.prototype.shift = function() {
-    return new ObjectPath(this.components.slice(1));
-  };
+    add(component) {
+      return new ObjectPath(this.components.concat([component]));
+    }
 
-  ObjectPath.prototype.depth = function() {
-    return this.components.length;
-  };
+    shift() {
+      return new ObjectPath(this.components.slice(1));
+    }
+
+    depth() {
+      return this.components.length;
+    }
+  }
 
   function formatPropertyAccess(prop) {
     if (typeof prop === 'number' || typeof prop === 'symbol') {
@@ -32,7 +34,7 @@ getJasmineRequireObj().ObjectPath = function(j$) {
       return '.' + prop;
     }
 
-    return "['" + prop + "']";
+    return `['${prop}']`;
   }
 
   function isValidIdentifier(string) {
diff --git a/src/core/matchers/toEqual.js b/src/core/matchers/toEqual.js
index d2db1bd8..9946d9ae 100644
--- a/src/core/matchers/toEqual.js
+++ b/src/core/matchers/toEqual.js
@@ -14,7 +14,7 @@ getJasmineRequireObj().toEqual = function(j$) {
         var result = {
             pass: false
           },
-          diffBuilder = j$.DiffBuilder({ prettyPrinter: matchersUtil.pp });
+          diffBuilder = new j$.DiffBuilder({ prettyPrinter: matchersUtil.pp });
 
         result.pass = matchersUtil.equals(actual, expected, diffBuilder);