fix: ensure durations are integers in json formatter

src/formatter/helpers/duration_helpers.ts

@@ -0,0 +1,7 @@
+import { Duration } from '@cucumber/messages'
+
+const NANOS_IN_SECOND = 1_000_000_000
+
+export function durationToNanoseconds(duration: Duration): number {
+  return Math.floor(duration.seconds * NANOS_IN_SECOND + duration.nanos)
+}

src/formatter/helpers/duration_helpers_spec.ts

@@ -0,0 +1,18 @@
+import { expect } from 'chai'
+import { durationToNanoseconds } from './duration_helpers'
+
+describe('duration helpers', () => {
+  describe('durationToNanoseconds', () => {
+    it('should convert under a second', () => {
+      expect(durationToNanoseconds({ seconds: 0, nanos: 257344166 })).to.eq(
+        257344166
+      )
+    })
+
+    it('should convert over a second', () => {
+      expect(durationToNanoseconds({ seconds: 2, nanos: 1043459 })).to.eq(
+        2001043459
+      )
+    })
+  })
+})

src/formatter/json_formatter.ts

@@ -8,6 +8,7 @@ import {
 import { ITestCaseAttempt } from './helpers/event_data_collector'
 import { doesHaveValue, doesNotHaveValue } from '../value_checker'
 import { parseStepArgument } from '../step_arguments'
+import { durationToNanoseconds } from './helpers/duration_helpers'
 
 const { getGherkinStepMap, getGherkinScenarioMap } = GherkinDocumentParser
 
@@ -280,10 +281,7 @@ export default class JsonFormatter extends Formatter {
       status: messages.TestStepResultStatus[status].toLowerCase(),
     }
     if (doesHaveValue(testStepResult.duration)) {
-      data.result.duration =
-        messages.TimeConversion.durationToMilliseconds(
-          testStepResult.duration
-        ) * 1000000
+      data.result.duration = durationToNanoseconds(testStepResult.duration)
     }
     if (
       status === messages.TestStepResultStatus.FAILED &&