Add flow type tests (#1230)

Closes #1224.

This adds flow-bin, adds it to the test running script, and adds some regression tests based on prior issues.

In an immediate proof of value (and proof of my own prior sloppiness) it spotted an issue that #1219 sought to fix and did not do so. Fix included along with test.

.flowconfig

@@ -0,0 +1,7 @@
+[ignore]
+<PROJECT_ROOT>/node_modules/.*
+<PROJECT_ROOT>/.*\.js$
+
+[options]
+emoji=true
+suppress_comment=\\(.\\|\n\\)*\\$ExpectError

index.js.flow

@@ -63,8 +63,8 @@ type AssertContext = {
 	};
 	// Assert that function doesn't throw an error or promise resolves.
 	notThrows: {
-		notThrows<U>(value: PromiseLike<U>, message?: string): Promise<U>;
-		notThrows(value: () => mixed, message?: string): void;
+		<U>(value: PromiseLike<U>, message?: string): Promise<U>;
+		(value: () => mixed, message?: string): void;
 	};
 	// Assert that contents matches regex.
 	regex(contents: string, regex: RegExp, message?: string): void;

package.json

@@ -43,7 +43,7 @@
     "node": ">=4"
   },
   "scripts": {
-    "test": "xo && nyc tap --no-cov --timeout=150 --jobs=4 test/*.js test/reporters/*.js",
+    "test": "xo && flow check && nyc tap --no-cov --timeout=150 --jobs=4 test/*.js test/reporters/*.js",
     "test-win": "tap --no-cov --reporter=classic --timeout=150 --jobs=4 test/*.js test/reporters/*.js",
     "visual": "node test/visual/run-visual-tests.js",
     "prepublish": "npm run make-ts",
@@ -167,6 +167,7 @@
     "coveralls": "^2.11.4",
     "delay": "^1.3.0",
     "execa": "^0.6.0",
+    "flow-bin": "^0.38.0",
     "get-stream": "^3.0.0",
     "git-branch": "^0.3.0",
     "has-ansi": "^2.0.0",

test/flow-types/regression-1114.js.flow

@@ -0,0 +1,53 @@
+/* @flow */
+
+const test = require('../../');
+
+test('Named test', t => {
+	t.pass('Success');
+	// $ExpectError: Unknown method "unknownAssertion"
+	t.unknownAssertion('Whoops');
+	const context = t.context;
+	// $ExpectError: Unknown method "end"
+	t.end();
+});
+
+test(t => {
+	t.pass('Success');
+	// $ExpectError: Unknown method "unknownAssertion"
+	t.unknownAssertion('Whoops');
+	const context = t.context;
+	// $ExpectError: Unknown method "end"
+	t.end();
+});
+
+test.cb(t => {
+	t.pass('Success');
+	t.end();
+});
+
+test.beforeEach(t => {
+	// $ExpectError: Unknown property "context"
+	const context = t.context;
+})
+
+function macro(t, input, expected) {
+	t.is(eval(input), expected);
+}
+macro.title = (title, input, expected) => title || input;
+
+function macro2(t, input, expected) {
+	t.is(eval(input), expected);
+}
+
+test('2 + 2 === 4', macro, '2 + 2', 4);
+test(macro, '2 * 3', 6);
+
+test('2 + 2 === 4', [macro, macro2], '2 + 2', 4);
+test([macro, macro2], '2 * 3', 6);
+
+function macroBadTitle(t, input, expected) {
+	t.is(eval(input), expected);
+}
+macroBadTitle.title = 'Not a function';
+// $ExpectError: Macro "title" is not a function
+test('2 + 2 === 4', macroBadTitle, '2 + 2', 4);

test/flow-types/regression-1148.js.flow

@@ -0,0 +1,19 @@
+/* @flow */
+
+const test = require('../../');
+
+test(t => {
+	t.throws(() => { throw new Error(); });
+	t.throws(Promise.reject(new Error()));
+
+	t.notThrows(() => { return; });
+	t.notThrows(Promise.resolve('Success'));
+
+	const error = t.throws(() => { throw new Error(); });
+	const message: string = error.message;
+
+	const promise = t.throws(Promise.reject(new Error()));
+	promise.then(error => {
+		const message: string = error.message;
+	})
+});