Make expect* throw useful errors outside tests.

Closes #132

[email protected]

Review URL: https://codereview.chromium.org//1148723005

Author: nex3

CHANGELOG.md

@@ -11,6 +11,9 @@
 * Add a heartbeat to reset a test's timeout whenever the test interacts with the
   test infrastructure.
 
+* `expect()`, `expectAsync()`, and `expectAsyncUntil()` throw more useful errors
+  if called outside a test body.
+
 ## 0.12.2
 
 * Convert JavaScript stack traces into Dart stack traces using source maps. This

lib/src/frontend/expect.dart

@@ -39,6 +39,10 @@ typedef String ErrorFormatter(
 /// [verbose] should be specified as `true`.
 void expect(actual, matcher,
     {String reason, bool verbose: false, ErrorFormatter formatter}) {
+  if (Invoker.current == null) {
+    throw new StateError("extend() may only be called within a test.");
+  }
+
   if (Invoker.current.closed) throw new ClosedException();
 
   matcher = wrapMatcher(matcher);

lib/src/frontend/expect_async.dart

@@ -220,8 +220,14 @@ class _ExpectedFunction {
 /// callback when debugging. [id] should be the name of the callback, while
 /// [reason] should be the reason the callback is expected to be called.
 Function expectAsync(Function callback,
-        {int count: 1, int max: 0, String id, String reason}) =>
-    new _ExpectedFunction(callback, count, max, id: id, reason: reason).func;
+        {int count: 1, int max: 0, String id, String reason}) {
+  if (Invoker.current == null) {
+    throw new StateError("expectAsync() may only be called within a test.");
+  }
+
+  return new _ExpectedFunction(callback, count, max, id: id, reason: reason)
+      .func;
+}
 
 /// Indicate that [callback] is expected to be called until [isDone] returns
 /// true.
@@ -235,5 +241,12 @@ Function expectAsync(Function callback,
 /// callback when debugging. [id] should be the name of the callback, while
 /// [reason] should be the reason the callback is expected to be called.
 Function expectAsyncUntil(Function callback, bool isDone(),
-    {String id, String reason}) => new _ExpectedFunction(callback, 0, -1,
-        id: id, reason: reason, isDone: isDone).func;
+    {String id, String reason}) {
+  if (Invoker.current == null) {
+    throw new StateError(
+        "expectAsyncUntil() may only be called within a test.");
+  }
+
+  return new _ExpectedFunction(callback, 0, -1,
+      id: id, reason: reason, isDone: isDone).func;
+}