feat: add basic plugin

packages/jest-core/src/plugins/FailedTestsInteractive.ts

@@ -0,0 +1,52 @@
+import type {AggregatedResult, AssertionLocation} from '@jest/test-result';
+import {BaseWatchPlugin, JestHookSubscriber, UsageData} from 'jest-watcher';
+
+export default class FailedTestsInteractivePlugin extends BaseWatchPlugin {
+  private _failedSnapshotTestAssertions?: Array<AssertionLocation>;
+
+  apply(hooks: JestHookSubscriber): void {
+    hooks.onTestRunComplete(results => {
+      this._failedSnapshotTestAssertions = this.getFailedSnapshotTestAssertions(
+        results,
+      );
+    });
+  }
+
+  getUsageInfo(): UsageData | null {
+    if (this._failedSnapshotTestAssertions?.length) {
+      return {key: 'i', prompt: 'run failing tests interactively'};
+    }
+
+    return null;
+  }
+
+  private getFailedSnapshotTestAssertions(
+    results: AggregatedResult,
+  ): Array<AssertionLocation> {
+    const failedTestPaths: Array<AssertionLocation> = [];
+
+    if (
+      // skip if no failed tests
+      results.numFailedTests === 0 ||
+      // skip if missing test results
+      !results.testResults ||
+      // skip if unmatched snapshots are present
+      results.snapshot.unmatched
+    ) {
+      return failedTestPaths;
+    }
+
+    results.testResults.forEach(testResult => {
+      testResult.testResults.forEach(result => {
+        if (result.status === 'failed') {
+          failedTestPaths.push({
+            fullName: result.fullName,
+            path: testResult.testFilePath,
+          });
+        }
+      });
+    });
+
+    return failedTestPaths;
+  }
+}

packages/jest-core/src/plugins/__tests__/FailedTestsInteractive.test.js

@@ -0,0 +1,28 @@
+import FailedTestsInteractivePlugin from '../FailedTestsInteractive';
+
+const MockFailedResults = {
+  snapshot: {},
+  testResults: [{testResults: [{status: 'failed'}]}],
+};
+
+describe('FailtedTestsInteractive', () => {
+  it('returns usage info when failing tests are present', () => {
+    expect(new FailedTestsInteractivePlugin({}).getUsageInfo()).toBeNull();
+
+    const activateablePlugin = new FailedTestsInteractivePlugin({});
+    let mockCallback;
+
+    activateablePlugin.apply({
+      onTestRunComplete: callback => {
+        mockCallback = callback;
+      },
+    });
+
+    mockCallback(MockFailedResults);
+
+    expect(activateablePlugin.getUsageInfo()).toEqual({
+      key: 'i',
+      prompt: 'run failing tests interactively',
+    });
+  });
+});

packages/jest-core/src/watch.ts

@@ -36,6 +36,7 @@ import {
   filterInteractivePlugins,
   getSortedUsageRows,
 } from './lib/watchPluginsHelpers';
+import FailedTestsInteractivePlugin from './plugins/FailedTestsInteractive';
 import QuitPlugin from './plugins/Quit';
 import TestNamePatternPlugin from './plugins/TestNamePattern';
 import TestPathPatternPlugin from './plugins/TestPathPattern';
@@ -58,6 +59,7 @@ const {print: preRunMessagePrint} = preRunMessage;
 let hasExitListener = false;
 
 const INTERNAL_PLUGINS = [
+  FailedTestsInteractivePlugin,
   TestPathPatternPlugin,
   TestNamePatternPlugin,
   UpdateSnapshotsPlugin,

packages/jest-watcher/src/BaseWatchPlugin.ts

@@ -13,7 +13,7 @@ import type {
   WatchPlugin,
 } from './types';
 
-class BaseWatchPlugin implements WatchPlugin {
+abstract class BaseWatchPlugin implements WatchPlugin {
   protected _stdin: NodeJS.ReadStream;
   protected _stdout: NodeJS.WriteStream;