🧪 Improve Test Coverage for Engine.greedyNextToken

echo-core-zig/src/inference/engine.zig

@@ -1015,4 +1015,27 @@ test "Engine.greedyNextToken correctly identifies token with max logit" {
     // Test early in the slice
     eng.logits[0] = 10.0;
     try std.testing.expectEqual(@as(u32, 0), eng.greedyNextToken());
+
+    // Edge case: all negative logits
+    eng.logits[0] = -5.0;
+    eng.logits[1] = -10.0;
+    eng.logits[2] = -2.0; // max is -2.0 at index 2
+    eng.logits[3] = -3.0;
+    try std.testing.expectEqual(@as(u32, 2), eng.greedyNextToken());
+
+    // Edge case: tie (should return the first one encountered)
+    eng.logits[0] = 1.0;
+    eng.logits[1] = 3.0; // max
+    eng.logits[2] = 3.0; // tie
+    eng.logits[3] = 2.0;
+    try std.testing.expectEqual(@as(u32, 1), eng.greedyNextToken());
+}
+
+test "Engine.decodeStep returns logits of expected length" {
+    const cfg = makeTinyConfig(0, 0);
+    var eng = try Engine.init(cfg, null, std.testing.allocator);
+    defer eng.deinit(std.testing.allocator);
+
+    const logits = try eng.decodeStep(0);
+    try std.testing.expectEqual(@as(usize, cfg.vocab_size), logits.len);
 }