[RFC]: Migrate from tape to in-house @stdlib/test/harness

Description

This RFC proposes

Proposal: Migrate stdlib Tests to In-House @stdlib/test/harness

This proposal delivers a tape-equivalent in-house test runner as @stdlib/test/harness, directly porting its minimal TAP API while matching @stdlib/bench/harness patterns. It eliminates the tape dep, supports only stdlib's used assertions (equal, strictEqual, ok, deepEqual, pass, fail, plan, end, test), and adds @stdlib/string/format interpolation—no parallelism, grouping, or extras like mocha/jest.

Before/After Test File

Before (tape):

'use strict';

var tape = require( 'tape' );
var foo = require( './../lib' );

tape( 'main export is a function', function test( t ) {
	t.ok( true, 'should be true' );
	t.strictEqual( typeof foo, 'function', 'main export is a function' );
	t.end();
});

tape( 'computes correctly', function test( t ) {
	t.plan( 2 );
	t.equal( foo( 3 ), 9, 'returns 9' );
	t.deepEqual( foo(  ),, 'deep equal' );[1][2][3]
	t.end();

After (@stdlib/test/harness):

After (@stdlib/test/harness):

```javascript
'use strict';

var test = require( '@stdlib/test/harness' );
var foo = require( './../lib' );

test( 'main export is a function', function test( t ) {
	t.ok( true, 'should be true' );
	t.strictEqual( typeof foo, 'function', 'main export is %s', 'function' );
	t.end();
});

test( 'computes correctly', function test( t ) {
	t.plan( 2 );
	t.equal( foo( 3 ), 9, 'returns %d', 9 );
	t.deepEqual( foo(  ),, 'deep equal' );[1][2][3]
	t.end();
});

Changes: Swap require('tape') → require('@stdlib/test/harness'). Assertions identical—no renames/refactors. Interpolation optional (%s/%d/%j via @stdlib/string/format).

Study of References

Reviewed tape source (tape-testing/tape): TAP stream via events, nested tests, async end(), assertion tracking. Compared to @stdlib/bench/harness: Similar b.bench()/test(), exports harness/stream factory, stdout TAP—no deps. Stdlib tests (e.g., Makefile/package.json scans): Use ~6 assertions max, plain TAP, no advanced tape features. Impl ports tape's core (test context, assert/incr count, TAP lines) to ~400 LOC Node streams.

Automation Strategy

• Publish @stdlib/test/harness (bench mirror: libtests, Makefile).
• Global replace: grep -rl "require('tape')" lib/ | xargs sed -i "s|require('tape')|require('@stdlib/test\/harness')|g" (handles escapes).
• Glob run: Update stdlib Makefile: $(QUIET) $(NODE) $(TOOLS_DIR)/harness.js $(shell find lib -name 'test.*.js').
• Validate: CI diff old/new TAP (tape | harness); fix interpolation mismatches via optional post-sed (regex scan t.equal/ok args).
• Coverage: Stick with istanbul (nyc/c8 drops Node 10-12 compat).

Related Issues

[Idea]: develop a project test runner

Questions

No.

Other

No.

Checklist

• I have read and understood the Code of Conduct.
• Searched for existing issues and pull requests.
• The issue name begins with RFC:.

Start by reading the proposed @stdlib/test/harness alongside the existing @stdlib/bench/harness patterns, then inspect lib test files, package.json, the stdlib Makefile, and tools/harness.js. Compare the current tape-based test execution and TAP output with the proposed harness; completion means the migration scope, supported assertions, and CI validation are agreed and working across the affected tests.