old_contents: 'use strict';
  
  function add (a, b) {
      console.assert(typeof a === 'number');
      assert(!isNaN(a));
      assert.equal(typeof b, 'number');
      assert.ok(!isNaN(b));
      return a + b;
  }
  
new_contents: 'use strict';
  
  function add (a, b) {
      console.assert(typeof a === 'number');
  
      assert(!isNaN(a));
      assert(!isNaN(a), 'assertion message');
  
      assert.ok(!isNaN(b));
      assert.ok(!isNaN(b), 'assertion message');
  
      assert.equal(typeof b, 'number');
      assert.equal(typeof b, 'number', 'assertion message');
  
      assert.strictEqual(typeof b, 'number');
      assert.strictEqual(typeof b, 'number', 'assertion message');
  
      assert.deepEqual(typeof b, 'number');
      assert.deepEqual(typeof b, 'number', 'assertion message');
  
      assert.deepStrictEqual(typeof b, 'number');
      assert.deepStrictEqual(typeof b, 'number', 'assertion message');
  
      assert.notEqual(typeof a, 'object');
      assert.notEqual(typeof a, 'object', 'assertion message');
  
      assert.notStrictEqual(typeof a, 'object');
      assert.notStrictEqual(typeof a, 'object', 'assertion message');
  
      assert.notDeepEqual(typeof a, 'object');
      assert.notDeepEqual(typeof a, 'object', 'assertion message');
  
      assert.notDeepStrictEqual(typeof a, 'object');
      assert.notDeepStrictEqual(typeof a, 'object', 'assertion message');
  
      assert.throws(function () {
          validate(a);
      });
      assert.throws(function () {
          validate(a);
      }, 'assertion message');
      assert.throws(function () {
          validate(a);
      }, Error, 'assertion message');
  
      assert.doesNotThrow(function () {
          validate(b);
      }, 'assertion message');
      assert.doesNotThrow(function () {
          validate(b);
      });
  
      assert.ifError(a);
      assert.fail(a, b, 'assertion message', '==');
      return a + b;
  }
  
subject: add comprehensive test patterns