What would be the simplest cross-environment JavaScript testing framework?

a.test.js

/*
	Pros: - intuitive syntax
	      - portable
	Cons: - always exits with 0, non-blocking
	      - legibility/alignment issues
*/

const testedFunction = (param) => {
	return param * 2;
};

// One test, one assertion
console.group('Default export');
console.log('Should multiply by two:\t', true &&
	testedFunction(3) === 6
);
console.groupEnd();

/* Output:
Default export
  Should multiply by two:	 true
*/

// One test, several assertions
console.group('Default export');
console.log('Should multiply by two:\t', true &&
	testedFunction(45) === 90
);
console.log('Should handle floats:\t', true &&
	testedFunction(0.0004) === 0.0008
);
console.groupEnd();

/* Output:
Default export
  Should multiply by two:	 true
  Should handle floats:	 true
*/

// Several tests
console.group('Test suite 1');
console.group('Default export');
console.log('Should multiply by two:\t', true &&
	testedFunction(12) === 14
);
console.group('Silly example');
console.log('Should be true:\t', true &&
	typeof 'foo' === 'string'
);
console.groupEnd();

/* Output:
Test suite 1
  Default export
    Should multiply by two:	 false
    Silly example
      Should be true:	 true
*/

b.test.js

/*
	Pros: - output is very legible
	      - exits with non-zero if a test fails
	Cons: - convoluted syntax, may require snippets
*/
const testedFunction = (param) => {
	return param * 2;
};

// One test, one assertion
console.group('Default export');

let t = 'Should multiply by two'; console.assert(
	testedFunction(3) === 6
, t) || console.log('✓\t', t);

console.groupEnd();

/* Output:
Default export
  ✓	 Should multiply by two
*/

// One test, several assertions
console.group('Default export');

t = 'Should multiply by two';
console.assert(
	testedFunction(45) === 90
, t) || console.log('✓\t', t);

t = 'Should handle floats';
console.assert(
	testedFunction(0.0004) === 0.0008
, t) || console.log('✓\t', t);

console.groupEnd();

/* Output:
Default export
  ✓	 Should multiply by two
  ✓	 Should handle floats
*/

// Several tests
console.group('Test suite 1');

console.group('Default export');

t = 'Should multiply by two';
console.assert(
	testedFunction(12) === 14
, t) || console.log('✓\t', t);

console.groupEnd();

/* Output:
Test suite 1
  Default export
assert.js:42
  throw new errors.AssertionError({
  ^

AssertionError [ERR_ASSERTION]: Should multiply by two
    [...]

shell returned 1
*/

c.test.js

/*
	Pros: - output is very legible
	Cons: - convoluted syntax, may require snippets
	      - doesn't exit with non-zero if a test fails
*/
const testedFunction = (param) => {
	return param * 2;
};

// One test, one assertion
console.group('Default export');

console.log((
  testedFunction(3) === 6
)?'✓':'✗','\t'+'Should multiply by two');

console.groupEnd();

/* Output:
Default export
  ✓	 Should multiply by two
*/

// One test, several assertions
console.group('Default export');

console.log((
  testedFunction(45) === 90
)?'✓':'✗','\t'+'Should multiply by two');

console.log((
  testedFunction(0.0004) === 0.0008
)?'✓':'✗','\t'+'Should handle floats');

console.groupEnd();

/* Output:
Default export
  ✓	 Should multiply by two
  ✓	 Should handle floats
*/