fix: use average of durations when merging (#163)

cypress/e2e/merge-timings.cy.js

@@ -0,0 +1,79 @@
+/// <reference types="cypress" />
+
+const { mergeSplitTimings } = require('../../src/timings')
+
+chai.config.truncateThreshold = 500
+
+it('averages the durations', () => {
+  const timings1 = {
+    durations: [
+      {
+        spec: 'cypress/integration/A.ts',
+        duration: 100,
+      },
+      {
+        spec: 'cypress/integration/B.ts',
+        duration: 80,
+      },
+    ],
+  }
+  const timings2 = {
+    durations: [
+      {
+        spec: 'cypress/integration/A.ts',
+        duration: 80,
+      },
+      {
+        spec: 'cypress/integration/B.ts',
+        duration: 100,
+      },
+    ],
+  }
+  const merged = mergeSplitTimings([timings1, timings2])
+  // the results are average
+  expect(merged).to.deep.equal({
+    durations: [
+      {
+        spec: 'cypress/integration/A.ts',
+        duration: 90,
+      },
+      {
+        spec: 'cypress/integration/B.ts',
+        duration: 90,
+      },
+    ],
+  })
+})
+
+it('takes existing values', () => {
+  const timings1 = {
+    durations: [
+      {
+        spec: 'cypress/integration/A.ts',
+        duration: 100,
+      },
+    ],
+  }
+  const timings2 = {
+    durations: [
+      {
+        spec: 'cypress/integration/B.ts',
+        duration: 20,
+      },
+    ],
+  }
+  const merged = mergeSplitTimings([timings1, timings2])
+  // the result has both entries
+  expect(merged).to.deep.equal({
+    durations: [
+      {
+        spec: 'cypress/integration/A.ts',
+        duration: 100,
+      },
+      {
+        spec: 'cypress/integration/B.ts',
+        duration: 20,
+      },
+    ],
+  })
+})

src/timings.js

@@ -113,8 +113,8 @@ function mergeSplitTimings(timings, debug = noop) {
       if (!specResults[item.spec]) {
         specResults[item.spec] = item.duration
       } else {
-        // pick the max spec duration
-        const maxDuration = Math.max(item.duration, specResults[item.spec])
+        // average the durations
+        const maxDuration = (item.duration + specResults[item.spec]) / 2
         specResults[item.spec] = maxDuration
       }
     })