2 files changed, 40 insertions, 2 deletions
diff --git a/cli/tests/unit/test_util.ts b/cli/tests/unit/test_util.ts
index ee924fe8a..65d23af65 100644
--- a/cli/tests/unit/test_util.ts
+++ b/cli/tests/unit/test_util.ts
@@ -39,7 +39,7 @@ interface UnitTestOptions {
   permissions?: UnitTestPermissions;
 }
 
-type TestFunction = () => void | Promise<void>;
+type TestFunction = (tester: Deno.TestContext) => void | Promise<void>;
 
 export function unitTest(fn: TestFunction): void;
 export function unitTest(options: UnitTestOptions, fn: TestFunction): void;
diff --git a/cli/tests/unit/testing_test.ts b/cli/tests/unit/testing_test.ts
index 89b3cc31f..144246002 100644
--- a/cli/tests/unit/testing_test.ts
+++ b/cli/tests/unit/testing_test.ts
@@ -1,5 +1,5 @@
 // Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
-import { assertThrows, unitTest } from "./test_util.ts";
+import { assertRejects, assertThrows, unitTest } from "./test_util.ts";
 
 unitTest(function testFnOverloading() {
   // just verifying that you can use this test definition syntax
@@ -25,3 +25,41 @@ unitTest(function nameOfTestCaseCantBeEmpty() {
     "The test name can't be empty",
   );
 });
+
+unitTest(function invalidStepArguments(t) {
+  assertRejects(
+    async () => {
+      // deno-lint-ignore no-explicit-any
+      await (t as any).step("test");
+    },
+    TypeError,
+    "Expected function for second argument.",
+  );
+
+  assertRejects(
+    async () => {
+      // deno-lint-ignore no-explicit-any
+      await (t as any).step("test", "not a function");
+    },
+    TypeError,
+    "Expected function for second argument.",
+  );
+
+  assertRejects(
+    async () => {
+      // deno-lint-ignore no-explicit-any
+      await (t as any).step();
+    },
+    TypeError,
+    "Expected a test definition or name and function.",
+  );
+
+  assertRejects(
+    async () => {
+      // deno-lint-ignore no-explicit-any
+      await (t as any).step(() => {});
+    },
+    TypeError,
+    "Expected a test definition or name and function.",
+  );
+});