fix(workers): skip loadTests in run() when suite is already populated

Worker threads call loadTests() in filterTests() before codecept.run().
A second loadTests() in run() duplicated Gherkin suites and executed each
assigned test twice (regression since ESM loadTests in #5640).

Add regression tests for JS and Gherkin worker assignments.

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: danielkrapiunitski-emplifi

lib/codecept.js

@@ -314,7 +314,12 @@ class Codecept {
       })
     }
 
-    await loadTests(mocha)
+    // Worker threads pre-load and filter tests before run(); reloading duplicates Gherkin suites.
+    if (!mocha.suite.total()) {
+      await loadTests(mocha)
+    } else {
+      mocha.lazyLoadFiles(true)
+    }
 
     return new Promise((resolve, reject) => {
       const done = async (failures) => {

test/data/sandbox/codecept.workers-gherkin.conf.js

@@ -0,0 +1,21 @@
+export const config = {
+  tests: './workers-gherkin/_placeholder.js',
+  timeout: 10000,
+  output: './output',
+  helpers: {
+    BDD: {
+      require: './support/bdd_helper.js',
+    },
+    Workers: {
+      require: './workers_helper.js',
+    },
+  },
+  gherkin: {
+    features: './workers-gherkin/*.feature',
+    steps: ['./workers-gherkin/steps.js'],
+  },
+  include: {},
+  bootstrap: false,
+  mocha: {},
+  name: 'sandbox-workers-gherkin',
+}

test/data/sandbox/workers-gherkin/_placeholder.js

@@ -0,0 +1 @@
+// Gherkin-only worker sandbox; JS tests path must exist for config.

test/data/sandbox/workers-gherkin/single.feature

@@ -0,0 +1,4 @@
+Feature: Worker gherkin single scenario
+
+  Scenario: runs once @worker_gherkin_once
+    Given I open a browser on a site

test/data/sandbox/workers-gherkin/steps.js

@@ -0,0 +1,3 @@
+import { Given } from '../../../../lib/mocha/bdd.js'
+
+Given('I open a browser on a site', () => {})

test/unit/worker_test.js

@@ -417,4 +417,56 @@ describe('Workers', function () {
     const actualFiles = testFiles.map(f => path.resolve(f))
     expect(actualFiles).to.deep.equal(expectedFiles, 'loadTests() should preserve original glob order without sorting')
   })
+
+  it('should run each assigned gherkin worker test once after pre-load', done => {
+    const workerConfig = {
+      by: 'test',
+      testConfig: './test/data/sandbox/codecept.workers-gherkin.conf.js',
+      options: {
+        grep: '@worker_gherkin_once',
+      },
+    }
+
+    let passedCount = 0
+    const workers = new Workers(1, workerConfig)
+
+    workers.on(event.test.passed, () => {
+      passedCount += 1
+    })
+
+    workers.run()
+
+    workers.on(event.all.result, result => {
+      expect(passedCount).to.equal(1)
+      expect(result.stats.tests).to.equal(1)
+      expect(result.stats.passes).to.equal(1)
+      done()
+    })
+  })
+
+  it('should run each assigned worker test once after pre-load (no duplicate loadTests in run)', done => {
+    const workerConfig = {
+      by: 'test',
+      testConfig: './test/data/sandbox/codecept.workers.conf.js',
+      options: {
+        grep: 'From worker @1_grep print message 1',
+      },
+    }
+
+    let passedCount = 0
+    const workers = new Workers(1, workerConfig)
+
+    workers.on(event.test.passed, () => {
+      passedCount += 1
+    })
+
+    workers.run()
+
+    workers.on(event.all.result, result => {
+      expect(passedCount).to.equal(1)
+      expect(result.stats.tests).to.equal(1)
+      expect(result.stats.passes).to.equal(1)
+      done()
+    })
+  })
 })