Test migration to jest by hand

Apparently using regular expressions is way easier.

test/isNull/isNull.test.js

@@ -0,0 +1,10 @@
+const expect = require('expect');
+const isNull = require('./isNull.js');
+
+
+  test('isNull is a Function', () => {
+  expect(isNull).toBeInstanceOf(Function);
+});
+  t.equal(isNull(null), true, "passed argument is a null");
+  t.equal(isNull(NaN), false, "passed argument is a null");
+