diff --git a/tests/cases/fourslash/getJavaScriptSemanticDiagnostics3.ts b/tests/cases/fourslash/getJavaScriptSemanticDiagnostics3.ts
index d74e97b36cc..c27308cd27c 100644
--- a/tests/cases/fourslash/getJavaScriptSemanticDiagnostics3.ts
+++ b/tests/cases/fourslash/getJavaScriptSemanticDiagnostics3.ts
@@ -2,7 +2,7 @@
 
 // @allowNonTsExtensions: true
 // @Filename: a.tsjs
-//// class C<T>;
+//// class C<T> { }
 
 verify.getSemanticDiagnostics(`[
   {
diff --git a/tests/cases/fourslash/getJavaScriptSemanticDiagnostics4.ts b/tests/cases/fourslash/getJavaScriptSemanticDiagnostics4.ts
new file mode 100644
index 00000000000..27635cb34b7
--- /dev/null
+++ b/tests/cases/fourslash/getJavaScriptSemanticDiagnostics4.ts
@@ -0,0 +1,15 @@
+/// <reference path="fourslash.ts" />
+
+// @allowNonTsExtensions: true
+// @Filename: a.tsjs
+//// public class C { }
+
+verify.getSemanticDiagnostics(`[
+  {
+    "message": "'public' can only be used in TypeScript.",
+    "start": 0,
+    "length": 6,
+    "category": "error",
+    "code": 8008
+  }
+]`);
\ No newline at end of file
diff --git a/tests/cases/fourslash/getJavaScriptSemanticDiagnostics5.ts b/tests/cases/fourslash/getJavaScriptSemanticDiagnostics5.ts
new file mode 100644
index 00000000000..9fd183b9e69
--- /dev/null
+++ b/tests/cases/fourslash/getJavaScriptSemanticDiagnostics5.ts
@@ -0,0 +1,15 @@
+/// <reference path="fourslash.ts" />
+
+// @allowNonTsExtensions: true
+// @Filename: a.tsjs
+//// class C implements D { }
+
+verify.getSemanticDiagnostics(`[
+  {
+    "message": "'implements clauses' can only be used in TypeScript.",
+    "start": 8,
+    "length": 12,
+    "category": "error",
+    "code": 8005
+  }
+]`);
\ No newline at end of file