v2: add 26B + 31B model tests (Phase 3)

Tests/01_Model/Model26BTest.swift

@@ -0,0 +1,65 @@
+import XCTest
+@testable import MarkBase
+
+final class Model26BTest: XCTestCase {
+
+    var engine: MarkBaseEngine!
+    var model: E4BModel!
+    let modelDir = "/Users/accusys/MarkBaseEngine/models/gemma-4-26b-standard"
+    let maxCtx = 128
+
+    override func setUp() {
+        super.setUp()
+        guard FileManager.default.fileExists(atPath: modelDir + "/model.safetensors") else {
+            return
+        }
+        engine = try? MarkBaseEngine(autoCompile: true)
+        model = try? E4BModel(modelDir: modelDir, engine: engine, maxContextLength: maxCtx)
+    }
+
+    func testModelLoads() throws {
+        try XCTSkipIf(model == nil, "gemma-4-26b-standard model not found")
+        XCTAssertNotNil(model)
+        XCTAssertEqual(model.hiddenSize, 2816)
+        XCTAssertEqual(model.numHiddenLayers, 30)
+        XCTAssertEqual(model.vocabSize, 262144)
+    }
+
+    func testBosTokenLogitsNoNaN() throws {
+        try XCTSkipIf(model == nil, "gemma-4-26b-standard model not found")
+        let logits = try model.forward(tokenId: 2, position: 0)
+        XCTAssertEqual(logits.count, model.vocabSize)
+        let nanCount = logits.filter { $0.isNaN }.count
+        XCTAssertEqual(nanCount, 0, "No NaN values in logits")
+    }
+
+    func testLogitsNotAllSaturated() throws {
+        try XCTSkipIf(model == nil, "gemma-4-26b-standard model not found")
+        let logits = try model.forward(tokenId: 2, position: 0)
+        // 26B has no softcapping, so logits should have variation
+        let uniqueCount = Set(logits.map { round($0 * 10) / 10 }).count
+        XCTAssertGreaterThan(uniqueCount, 100, "Logits should have meaningful variation")
+    }
+
+    func testLogitsReasonableRange() throws {
+        try XCTSkipIf(model == nil, "gemma-4-26b-standard model not found")
+        let logits = try model.forward(tokenId: 2, position: 0)
+        let maxVal = logits.max() ?? 0
+        let minVal = logits.min() ?? 0
+        XCTAssertGreaterThan(maxVal, -100)
+        XCTAssertLessThan(maxVal, 10000)
+        XCTAssertGreaterThan(minVal, -10000)
+        XCTAssertLessThan(minVal, 100)
+        XCTAssertGreaterThan(maxVal, minVal, "Logits should have dynamic range")
+    }
+
+    func testMultipleTokensProduceDifferentLogits() throws {
+        try XCTSkipIf(model == nil, "gemma-4-26b-standard model not found")
+        let tokens = [2, 100, 1000, 10000]
+        for (pos, tokenId) in tokens.enumerated() {
+            let logits = try model.forward(tokenId: tokenId, position: pos)
+            let nanCount = logits.filter { $0.isNaN }.count
+            XCTAssertEqual(nanCount, 0, "NaN for token=\(tokenId) pos=\(pos)")
+        }
+    }
+}