text: var test = require("tape")
  var extend = require("./")
  var mutableExtend = require("./mutable")
  
  test("merge", function(assert) {
      var a = { a: "foo" }
      var b = { b: "bar" }
  
      assert.deepEqual(extend(a, b), { a: "foo", b: "bar" })
      assert.end()
  })
  
  test("replace", function(assert) {
      var a = { a: "foo" }
      var b = { a: "bar" }
  
      assert.deepEqual(extend(a, b), { a: "bar" })
      assert.end()
  })
  
  test("undefined", function(assert) {
      var a = { a: undefined }
      var b = { b: "foo" }
  
      assert.deepEqual(extend(a, b), { a: undefined, b: "foo" })
      assert.deepEqual(extend(b, a), { a: undefined, b: "foo" })
      assert.end()
  })
  
  test("handle 0", function(assert) {
      var a = { a: "default" }
      var b = { a: 0 }
  
      assert.deepEqual(extend(a, b), { a: 0 })
      assert.deepEqual(extend(b, a), { a: "default" })
      assert.end()
  })
  
  test("is immutable", function (assert) {
      var record = {}
  
      extend(record, { foo: "bar" })
      assert.equal(record.foo, undefined)
      assert.end()
  })
  
  test("null as argument", function (assert) {
      var a = { foo: "bar" }
      var b = null
      var c = void 0
  
      assert.deepEqual(extend(b, a, c), { foo: "bar" })
      assert.end()
  })
  
  test("mutable", function (assert) {
      var a = { foo: "bar" }
  
      mutableExtend(a, { bar: "baz" })
  
      assert.equal(a.bar, "baz")
      assert.end()
  })
  