Merge pull request #163 from DEFRA/BAU-dynamic-runner-count-update

BAU: dynamic runner count update

.eslintrc.cjs

@@ -132,6 +132,7 @@ module.exports = {
         'plugin:jest/style'
       ],
       files: ['**/*.test.{cjs,js}', '**/__mocks__/**'],
+      excludedFiles: ['**/user-journey-tests/**/*.{cjs,js}'],
       plugins: ['jest'],
       rules: {
         // Allow Jest to assert on mocked unbound methods

jest.config.js

@@ -7,7 +7,7 @@ export default {
   resetModules: true,
   clearMocks: true,
   silent: false,
-  testMatch: ['**/src/**/*.test.js'],
+  testMatch: ['**/src/**/*.test.js', '**/user-journey-tests/config/*.test.js'],
   reporters: ['default', ['github-actions', { silent: false }], 'summary'],
   setupFilesAfterEnv: ['<rootDir>/.jest/setup.js'],
   collectCoverageFrom: ['src/**/*.js'],

user-journey-tests/config/browserstackMetrics.js

@@ -1,4 +1,4 @@
-const defaultMaximum = 6
+const preferredMinimum = 6
 
 export const getBrowserStackRunners = async () => {
   const username = process.env.BROWSERSTACK_USER
@@ -24,18 +24,23 @@ export const getBrowserStackRunners = async () => {
       parallel_sessions_running: threadsRunning
     } = data
     const availableThreads = threadsAllowed - threadsRunning
-    const threadsToUse = Math.floor(availableThreads / 2)
 
-    if (threadsToUse < defaultMaximum && threadsToUse < availableThreads) {
-      return threadsToUse
-    }
+    return recommendRunnerCount({ availableThreads })
+  } catch (error) {
+    return preferredMinimum // default to a speculative value
+  }
+}
 
-    if (defaultMaximum > availableThreads) {
-      return availableThreads
-    }
+export const recommendRunnerCount = ({ availableThreads }) => {
+  const threadsToUse = Math.floor(availableThreads / 2)
 
-    return defaultMaximum
-  } catch (error) {
-    return defaultMaximum // default to a speculative value
+  if (availableThreads < preferredMinimum) {
+    return availableThreads
+  }
+
+  if (threadsToUse < preferredMinimum) {
+    return preferredMinimum
   }
+
+  return threadsToUse
 }

user-journey-tests/config/browserstackMetrics.test.js

@@ -0,0 +1,17 @@
+import { recommendRunnerCount } from './browserstackMetrics'
+
+describe('recommendRunnerCount', () => {
+  it('should take half availableThreads runners if that figure is greater than the minimum preferred', () => {
+    expect(recommendRunnerCount({ availableThreads: 16 })).toBe(8)
+    expect(recommendRunnerCount({ availableThreads: 15 })).toBe(7)
+  })
+
+  it('should take the minimum preferred if half availableThreads runners is too small, but available runners is more than minimum preferred', () => {
+    expect(recommendRunnerCount({ availableThreads: 10 })).toBe(6)
+    expect(recommendRunnerCount({ availableThreads: 8 })).toBe(6)
+  })
+
+  it('should take all that remains if the availableThreads is below minimum preferred', () => {
+    expect(recommendRunnerCount({ availableThreads: 4 })).toBe(4)
+  })
+})