Runtime Manual/Developer Tooling/Testing, Coverage & Benchmarking (amber test & amber bench)

Testing, Coverage & Benchmarking (amber test & amber bench)

Built-in Jest-compatible test runner, LCOV coverage reporting, microbenchmark suite & CPU flamecharts

In production and performance-sensitive systems, quality tests, code coverage metrics, and microbenchmarks are essential. Amber provides native tools without needing Jest, Vitest, or C8.

1. Automated Testing & Code Coverage (`amber test --coverage`)

Amber features a native test runner supporting Jest and Vitest syntax.

1.1 Running Tests

code

# Run all *.test.ts and *.spec.js files
$ amber test

# Run a specific test file
$ amber test tests/auth.test.ts

1.2 Collecting Code Coverage (`--coverage`)

Add the --coverage flag to track line-level coverage. Amber outputs an aligned summary table to the console and generates a standard coverage/lcov.info file (ready for Codecov, Coveralls, or CI):

code

$ amber test --coverage

Output:

code

=============================== Coverage summary ===============================
Statements   : 96.42% ( 538/558 )
Branches     : 91.17% ( 155/170 )
Functions    : 98.24% ( 112/114 )
Lines        : 96.42% ( 538/558 )
================================================================================
📄 LCOV report saved to: coverage/lcov.info

2. Language-Level Microbenchmarks (`amber bench`)

To measure the impact of algorithm tweaks, parsing, or math operations, use amber bench.

2.1 Writing a Benchmark File

Create *.bench.ts or *.bench.js files:

code

// math.bench.ts
bench("JSON.parse small payload", () => {
  JSON.parse('{"id": 1, "name": "amberjs", "ok": true}');
});

bench("Array sort 1000 items", () => {
  const arr = Array.from({ length: 1000 }, (_, i) => 1000 - i);
  arr.sort((a, b) => a - b);
});

2.2 Running Benchmarks

code

$ amber bench
# Or specify a directory pattern
$ amber bench benchmarks/

Console output:

code

🚀 Running benchmarks...

  Benchmark                          Iterations   Avg Time (ns)   Throughput (ops/s)
  ──────────────────────────────────────────────────────────────────────────────────
  JSON.parse small payload               10,000          412 ns        2,427,184/s
  Array sort 1000 items                   2,000       12,850 ns           77,821/s

✨ All benchmarks completed in 42.8ms.

3. V8 CPU Profiling (`amber profile`)

Diagnose CPU hotspots and bottlenecks with microsecond precision using amber profile, which exports Chrome DevTools compliant .cpuprofile files.

3.1 Capturing a Profile

code

# Execute and profile app.ts
$ amber profile app.ts -o app.cpuprofile

3.2 Visualizing Flamecharts in Chrome

Open Google Chrome or Chromium;
Press F12 to open DevTools and navigate to the Performance or Memory panel;
Click Load profile... and select app.cpuprofile;
Interactively zoom into the flamechart, inspect function self-times, and trace call trees.

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