Add .toBeNullish matcher

lib/jasmine-core/jasmine.js

@@ -150,6 +150,7 @@ getJasmineRequireObj().requireMatchers = function(jRequire, j$) {
       'toBeTrue',
       'toBeTruthy',
       'toBeUndefined',
+      'toBeNullish',
       'toContain',
       'toEqual',
       'toHaveSize',

spec/core/matchers/toBeNullishSpec.js

@@ -0,0 +1,19 @@
+describe('toBeNullish', function() {
+  it('passes for null values', function() {
+    const matcher = jasmineUnderTest.matchers.toBeNullish();
+    const result = matcher.compare(null);
+    expect(result.pass).toBe(true);
+  });
+
+  it('passes for undefined values', function() {
+    const matcher = jasmineUnderTest.matchers.toBeNullish();
+    const result = matcher.compare(void 0);
+    expect(result.pass).toBe(true);
+  });
+
+  it('fails when matching defined values', function() {
+    const matcher = jasmineUnderTest.matchers.toBeNullish();
+    const result = matcher.compare('foo');
+    expect(result.pass).toBe(false);
+  });
+});

src/core/matchers/toBeNullish.js

@@ -0,0 +1,21 @@
+getJasmineRequireObj().toBeNullish = function() {
+  /**
+   * {@link expect} the actual value to be `null` or `undefined`.
+   * @function
+   * @name matchers#toBeNullish
+   * @since 5.6.0
+   * @example
+   * expect(result).toBeNullish():
+   */
+  function toBeNullish() {
+    return {
+      compare: function(actual) {
+        return {
+          pass: null === actual || void 0 === actual
+        };
+      }
+    };
+  }
+
+  return toBeNullish;
+};