updated

test/logger.test.js

@@ -0,0 +1,67 @@
+import { test } from 'node:test';
+import assert from 'node:assert/strict';
+import { spawnSync } from 'node:child_process';
+
+// Regression test: the logger must produce real JSON lines, not the
+// literal string "undefined" (a bug caused by passing JSON.stringify a
+// replacer *factory* instead of calling it first).
+test('logger prints a parseable JSON object with the expected fields, not "undefined"', () => {
+  const script = `
+    import { createLogger } from '${import.meta.resolve('../src/logger.js').replace('file://', '')}';
+    createLogger({ component: 'x' }).info('hello', { foo: 'bar' });
+  `;
+  const result = spawnSync(process.execPath, ['--input-type=module', '-e', script], { encoding: 'utf8' });
+  assert.equal(result.status, 0, result.stderr);
+  const line = result.stdout.trim();
+  assert.notEqual(line, 'undefined');
+  const parsed = JSON.parse(line);
+  assert.equal(parsed.level, 'info');
+  assert.equal(parsed.msg, 'hello');
+  assert.equal(parsed.component, 'x');
+  assert.equal(parsed.foo, 'bar');
+  assert.ok(parsed.time);
+});
+
+test('logger.child merges bindings and does not mutate the parent', () => {
+  const script = `
+    import { createLogger } from '${import.meta.resolve('../src/logger.js').replace('file://', '')}';
+    const parent = createLogger({ a: 1 });
+    const child = parent.child({ b: 2 });
+    child.info('from child');
+    parent.info('from parent');
+  `;
+  const result = spawnSync(process.execPath, ['--input-type=module', '-e', script], { encoding: 'utf8' });
+  assert.equal(result.status, 0, result.stderr);
+  const [childLine, parentLine] = result.stdout.trim().split('\n').map((l) => JSON.parse(l));
+  assert.deepEqual({ a: childLine.a, b: childLine.b }, { a: 1, b: 2 });
+  assert.equal(parentLine.b, undefined);
+});
+
+test('debug messages are suppressed at the default (info) log level', () => {
+  const script = `
+    import { createLogger } from '${import.meta.resolve('../src/logger.js').replace('file://', '')}';
+    createLogger({}).debug('should not appear');
+    createLogger({}).info('should appear');
+  `;
+  const result = spawnSync(process.execPath, ['--input-type=module', '-e', script], {
+    encoding: 'utf8',
+    env: { ...process.env, LOG_LEVEL: 'info' },
+  });
+  assert.equal(result.status, 0, result.stderr);
+  const lines = result.stdout.trim().split('\n').filter(Boolean);
+  assert.equal(lines.length, 1);
+  assert.equal(JSON.parse(lines[0]).msg, 'should appear');
+});
+
+test('errors are logged with name/message/stack, not serialized to {}', () => {
+  const script = `
+    import { createLogger } from '${import.meta.resolve('../src/logger.js').replace('file://', '')}';
+    createLogger({}).error('boom', { error: new Error('bad thing') });
+  `;
+  const result = spawnSync(process.execPath, ['--input-type=module', '-e', script], { encoding: 'utf8' });
+  assert.equal(result.status, 0, result.stderr);
+  const parsed = JSON.parse(result.stderr.trim());
+  assert.equal(parsed.error.message, 'bad thing');
+  assert.equal(parsed.error.name, 'Error');
+  assert.ok(parsed.error.stack);
+});