tests: add unit tests for sync true to ThreadStream

test/transport/syncTrue.test.js

@@ -0,0 +1,55 @@
+'use strict'
+
+const pino = require('../..')
+const { join } = require('node:path')
+const { readFileSync } = require('node:fs')
+const { test } = require('tap')
+const { file } = require('../helper')
+
+test('thread-stream sync true should log synchronously', async (t) => {
+  const outputPath = file()
+
+  function getOutputLogLines () {
+    return (readFileSync(outputPath)).toString().trim().split('\n').map(JSON.parse)
+  }
+
+  const transport = pino.transport({
+    target: join(__dirname, '..', 'fixtures', 'to-file-transport.js'),
+    options: { destination: outputPath },
+    sync: true
+  })
+  const instance = pino(transport)
+
+  var value = { message: 'sync' }
+  instance.info(value)
+  instance.info(value)
+  instance.info(value)
+  instance.info(value)
+  instance.info(value)
+  instance.info(value)
+  let interrupt = false
+  let flushData
+  let loopCounter = 0
+
+  // Start a synchronous loop
+  while (!interrupt && loopCounter < (process.env.MAX_TEST_LOOP_ITERATION || 5000)) {
+    try {
+      loopCounter++
+      const data = getOutputLogLines()
+      flushData = data
+      if (data) {
+        interrupt = true
+        break
+      }
+    } catch (error) {
+      // File may not exist yet
+      // Wait till MAX_TEST_LOOP_ITERATION iterations
+    }
+  }
+
+  if (!interrupt) {
+    throw new Error('Sync loop did not get interrupt')
+  }
+
+  t.equal(flushData.length, 6)
+})