Support parallel runs that do not need to run test files

lib/reporters/verbose.js

@@ -90,6 +90,7 @@ class VerboseReporter {
 		this.failFastEnabled = plan.failFastEnabled;
 		this.matching = plan.matching;
 		this.previousFailures = plan.previousFailures;
+		this.emptyParallelRun = plan.status.emptyParallelRun;
 
 		if (this.watching || plan.files.length > 1) {
 			this.prefixTitle = (testFile, title) => prefixTitle(plan.filePathPrefix, testFile, title);
@@ -320,6 +321,12 @@ class VerboseReporter {
 	}
 
 	endRun() { // eslint-disable-line complexity
+		if (this.emptyParallelRun) {
+			this.lineWriter.writeLine('No files tested in this parallel run');
+			this.lineWriter.writeLine();
+			return;
+		}
+
 		if (!this.stats) {
 			this.lineWriter.writeLine(colors.error(`${figures.cross} Couldn’t find any files to test`));
 			this.lineWriter.writeLine();

lib/run-status.js

@@ -8,6 +8,11 @@ class RunStatus extends Emittery {
 
 		this.pendingTests = new Map();
 
+		this.emptyParallelRun = parallelRuns &&
+			parallelRuns.currentFileCount === 0 &&
+			parallelRuns.totalRuns > 1 &&
+			files > 0;
+
 		this.stats = {
 			byFile: new Map(),
 			declaredTests: 0,
@@ -143,6 +148,10 @@ class RunStatus extends Emittery {
 	}
 
 	suggestExitCode(circumstances) {
+		if (this.emptyParallelRun) {
+			return 0;
+		}
+
 		if (circumstances.matching && this.stats.selectedTests === 0) {
 			return 1;
 		}

test-tap/fixture/parallel-runs/2.js → test-tap/fixture/parallel-runs/less-files-than-ci-total/2.js

@@ -1,4 +1,4 @@
-const test = require('../../..');
+const test = require('../../../..');
 
 test('at expected index', t => {
 	t.is(process.env.CI_NODE_INDEX, '0');

test-tap/fixture/parallel-runs/less-files-than-ci-total/9.js

@@ -0,0 +1,5 @@
+const test = require('../../../..');
+
+test('at expected index', t => {
+	t.is(process.env.CI_NODE_INDEX, '1');
+});

test-tap/fixture/parallel-runs/10.js → test-tap/fixture/parallel-runs/more-files-than-ci-total/10.js

@@ -1,4 +1,4 @@
-const test = require('../../..');
+const test = require('../../../..');
 
 test('at expected index', t => {
 	t.is(process.env.CI_NODE_INDEX, '1');

test-tap/fixture/parallel-runs/more-files-than-ci-total/2.js

@@ -0,0 +1,5 @@
+const test = require('../../../..');
+
+test('at expected index', t => {
+	t.is(process.env.CI_NODE_INDEX, '0');
+});

test-tap/fixture/parallel-runs/2a.js → test-tap/fixture/parallel-runs/more-files-than-ci-total/2a.js

@@ -1,4 +1,4 @@
-const test = require('../../..');
+const test = require('../../../..');
 
 test('at expected index', t => {
 	t.is(process.env.CI_NODE_INDEX, '0');

test-tap/fixture/parallel-runs/9.js → test-tap/fixture/parallel-runs/more-files-than-ci-total/9.js

@@ -1,4 +1,4 @@
-const test = require('../../..');
+const test = require('../../../..');
 
 test('at expected index', t => {
 	t.is(process.env.CI_NODE_INDEX, '0');

test-tap/fixture/parallel-runs/Ab.js → test-tap/fixture/parallel-runs/more-files-than-ci-total/Ab.js

@@ -1,5 +1,5 @@
 /* eslint-disable unicorn/filename-case */
-const test = require('../../..');
+const test = require('../../../..');
 
 test('at expected index', t => {
 	t.is(process.env.CI_NODE_INDEX, '1');

test-tap/fixture/parallel-runs/a.js → test-tap/fixture/parallel-runs/more-files-than-ci-total/a.js

@@ -1,4 +1,4 @@
-const test = require('../../..');
+const test = require('../../../..');
 
 test('at expected index', t => {
 	t.is(process.env.CI_NODE_INDEX, '1');

test-tap/fixture/parallel-runs/b.js → test-tap/fixture/parallel-runs/more-files-than-ci-total/b.js

@@ -1,4 +1,4 @@
-const test = require('../../..');
+const test = require('../../../..');
 
 test('at expected index', t => {
 	t.is(process.env.CI_NODE_INDEX, '2');

test-tap/fixture/parallel-runs/c.js → test-tap/fixture/parallel-runs/more-files-than-ci-total/c.js

@@ -1,4 +1,4 @@
-const test = require('../../..');
+const test = require('../../../..');
 
 test('at expected index', t => {
 	t.is(process.env.CI_NODE_INDEX, '2');

test-tap/fixture/parallel-runs/more-files-than-ci-total/package.json

@@ -0,0 +1,5 @@
+{
+	"ava": {
+		"files": ["*.js"]
+	}
+}

test-tap/fixture/parallel-runs/no-files/package.json

@@ -0,0 +1,5 @@
+{
+	"ava": {
+		"files": ["*.js"]
+	}
+}

test-tap/integration/parallel-runs.js

@@ -2,11 +2,11 @@
 const {test} = require('tap');
 const {execCli} = require('../helper/cli');
 
-test('correctly distributes the test files', t => {
+test('correctly distributes more test files than CI_NODE_TOTAL', t => {
 	t.plan(3);
 	for (let i = 0; i < 3; i++) {
 		execCli([], {
-			dirname: 'fixture/parallel-runs',
+			dirname: 'fixture/parallel-runs/more-files-than-ci-total',
 			env: {
 				AVA_FORCE_CI: 'ci',
 				CI_NODE_INDEX: String(i),
@@ -15,3 +15,31 @@ test('correctly distributes the test files', t => {
 		}, err => t.ifError(err));
 	}
 });
+
+test('correctly distributes less test files than CI_NODE_TOTAL', t => {
+	t.plan(3);
+	for (let i = 0; i < 3; i++) {
+		execCli([], {
+			dirname: 'fixture/parallel-runs/less-files-than-ci-total',
+			env: {
+				AVA_FORCE_CI: 'ci',
+				CI_NODE_INDEX: String(i),
+				CI_NODE_TOTAL: '3'
+			}
+		}, err => t.ifError(err));
+	}
+});
+
+test('fail when there are no files', t => {
+	t.plan(3);
+	for (let i = 0; i < 3; i++) {
+		execCli([], {
+			dirname: 'fixture/parallel-runs/no-files',
+			env: {
+				AVA_FORCE_CI: 'ci',
+				CI_NODE_INDEX: String(i),
+				CI_NODE_TOTAL: '3'
+			}
+		}, err => t.ok(err));
+	}
+});