Add test for grep option programmatic (#188)

* - add test for grep option programmatic

* Update according comments to pull request:
- change body of test
- rename test name

test/grep/README

@@ -1 +1,2 @@
-Check that --grep flag run tests by string pattern 'grep'
+- index.js check that --grep flag run tests by string pattern 'grep'
+- indexProgrammatic.js check that --grep flag run tests by string pattern 'grep' with programmatic using mocha

test/grep/index.js

@@ -22,6 +22,5 @@ exec(libExecutable + ' -R json --grep grep test/grep/tests', {
         process.exit(1);
     }
 
-    assert.strictEqual(jsonReporterOutput.stats.passes, 3, 'Tests number is wrong. Expected 3. Actual: '
-      + jsonReporterOutput.stats.passes);
+    assert.strictEqual(jsonReporterOutput.stats.passes, 3);
 });

test/grep/indexProgrammatic.js

@@ -0,0 +1,21 @@
+#!/usr/bin/env node
+
+'use strict';
+
+const assert = require('assert');
+const MochaParallelTests = require('../../dist/main/mocha').default;
+const { setProcessExitListeners } = require('../../dist/util');
+const SilentReporter = require('../util/silent-reporter');
+
+setProcessExitListeners();
+
+const mocha = new MochaParallelTests;
+mocha.addFile(`${__dirname}/tests/test.js`)
+    .addFile(`${__dirname}/tests/test1.js`)
+    .timeout(10000)
+    .grep('grep')
+    .reporter(SilentReporter);
+
+mocha.run().on('end', function () {
+    assert.strictEqual(this.stats.passes, 3);
+});

test/index.sh

@@ -77,6 +77,7 @@ test 'subprocess exits before sending an end message' test/no-subprocess-end/ind
 test 'unhandled rejections should not force subprocess to exit' test/q-promises/index.js
 test 'uncaught exceptions should not force subprocess to exit' test/uncaught-exception/index.js
 test 'grep option' test/grep/index.js
+test 'grep option - programmatic API support' test/grep/indexProgrammatic.js
 
 echo "Passes: $PASSES Failes: $FAILES"
 echo ""