feat(cli): enable timestamped run output by default

src/cli/run/timestamp-output.test.ts

@@ -0,0 +1,127 @@
+/// <reference types="bun-types" />
+
+import { describe, expect, it } from "bun:test"
+import { createTimestampTransformer, createTimestampedStdoutController } from "./timestamp-output"
+
+interface MockWriteStream {
+  write: (
+    chunk: Uint8Array | string,
+    encodingOrCallback?: BufferEncoding | ((error?: Error | null) => void),
+    callback?: (error?: Error | null) => void,
+  ) => boolean
+  writes: string[]
+}
+
+function createMockWriteStream(): MockWriteStream {
+  const writes: string[] = []
+
+  const write: MockWriteStream["write"] = (
+    chunk,
+    encodingOrCallback,
+    callback,
+  ) => {
+    const text = typeof chunk === "string"
+      ? chunk
+      : Buffer.from(chunk).toString(typeof encodingOrCallback === "string" ? encodingOrCallback : undefined)
+
+    writes.push(text)
+
+    if (typeof encodingOrCallback === "function") {
+      encodingOrCallback(null)
+    } else if (callback) {
+      callback(null)
+    }
+
+    return true
+  }
+
+  return { write, writes }
+}
+
+describe("createTimestampTransformer", () => {
+  it("prefixes each output line with timestamp", () => {
+    // given
+    const now = () => new Date("2026-02-19T12:34:56.000Z")
+    const transform = createTimestampTransformer(now)
+
+    // when
+    const output = transform("hello\nworld")
+
+    // then
+    expect(output).toBe("[12:34:56] hello\n[12:34:56] world")
+  })
+
+  it("keeps line-start state across chunk boundaries", () => {
+    // given
+    const now = () => new Date("2026-02-19T01:02:03.000Z")
+    const transform = createTimestampTransformer(now)
+
+    // when
+    const first = transform("hello")
+    const second = transform(" world")
+    const third = transform("\nnext")
+
+    // then
+    expect(first).toBe("[01:02:03] hello")
+    expect(second).toBe(" world")
+    expect(third).toBe("\n[01:02:03] next")
+  })
+
+  it("returns empty string for empty chunk", () => {
+    // given
+    const transform = createTimestampTransformer(() => new Date("2026-02-19T01:02:03.000Z"))
+
+    // when
+    const output = transform("")
+
+    // then
+    expect(output).toBe("")
+  })
+})
+
+describe("createTimestampedStdoutController", () => {
+  it("prefixes stdout writes when enabled", () => {
+    // given
+    const stdout = createMockWriteStream()
+    const controller = createTimestampedStdoutController(stdout as unknown as NodeJS.WriteStream)
+
+    // when
+    controller.enable()
+    stdout.write("hello\nworld")
+
+    // then
+    expect(stdout.writes).toHaveLength(1)
+    expect(stdout.writes[0]!).toMatch(/^\[\d{2}:\d{2}:\d{2}\] hello\n\[\d{2}:\d{2}:\d{2}\] world$/)
+  })
+
+  it("restores original write function", () => {
+    // given
+    const stdout = createMockWriteStream()
+    const controller = createTimestampedStdoutController(stdout as unknown as NodeJS.WriteStream)
+    controller.enable()
+
+    // when
+    stdout.write("before restore")
+    controller.restore()
+    stdout.write("after restore")
+
+    // then
+    expect(stdout.writes).toHaveLength(2)
+    expect(stdout.writes[0]!).toMatch(/^\[\d{2}:\d{2}:\d{2}\] before restore$/)
+    expect(stdout.writes[1]).toBe("after restore")
+  })
+
+  it("supports Uint8Array chunks and encoding", () => {
+    // given
+    const stdout = createMockWriteStream()
+    const controller = createTimestampedStdoutController(stdout as unknown as NodeJS.WriteStream)
+
+    // when
+    controller.enable()
+    stdout.write(Buffer.from("byte line"), "utf8")
+
+    // then
+    expect(stdout.writes).toHaveLength(1)
+    expect(stdout.writes[0]!).toMatch(/^\[\d{2}:\d{2}:\d{2}\] byte line$/)
+  })
+})