Directly run the test if the pattern directly resolves to a file

Summary:Directly run a test when passing path to a file instead of treating it as a pattern.
Also avoid sorting the paths if there's only a single path, as we were doing a lot of things in the `_sortTests` method.
Closes jestjs#810

Differential Revision: D3063643

fb-gh-sync-id: 4c9abd1c5b630e8e68641bf515b9ea1f2ce9fab2
fbshipit-source-id: 4c9abd1c5b630e8e68641bf515b9ea1f2ce9fab2

Author: kentaromiura

src/TestRunner.js

@@ -214,8 +214,14 @@ class TestRunner {
   }
 
   promiseTestPathsMatching(pathPattern) {
-    return this._getAllTestPaths()
-      .then(paths => paths.filter(path => pathPattern.test(path)));
+    try {
+      const maybeFile = path.resolve(process.cwd(), pathPattern);
+      fs.accessSync(maybeFile);
+      return Promise.resolve([pathPattern].filter(this._isTestFilePath));
+    } catch (e) {
+      return this._getAllTestPaths()
+        .then(paths => paths.filter(path => new RegExp(pathPattern).test(path)));
+    }
   }
 
   _getTestPerformanceCachePath() {

src/jest.js

@@ -47,7 +47,7 @@ function getTestPaths(testRunner, config, patternInfo) {
   if (patternInfo.onlyChanged) {
     return findOnlyChangedTestPaths(testRunner, config);
   } else {
-    return testRunner.promiseTestPathsMatching(new RegExp(patternInfo.pattern));
+    return testRunner.promiseTestPathsMatching(patternInfo.pattern);
   }
 }