Add tests for Temporal.now.instant (#3031)

test/built-ins/Temporal/now/instant/extensible.js

@@ -0,0 +1,9 @@
+// Copyright (C) 2021 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+esid: sec-temporal.now.instant
+description: Temporal.now.instant is extensible.
+features: [Temporal]
+---*/
+
+assert(Object.isExtensible(Temporal.now.instant));

test/built-ins/Temporal/now/instant/length.js

@@ -0,0 +1,15 @@
+// Copyright (C) 2021 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+esid: sec-temporal.now.instant
+description: Temporal.now.instant.length is 0
+includes: [propertyHelper.js]
+features: [Temporal]
+---*/
+
+verifyProperty(Temporal.now.instant, "length", {
+  value: 0,
+  writable: false,
+  enumerable: false,
+  configurable: true,
+});

test/built-ins/Temporal/now/instant/name.js

@@ -0,0 +1,16 @@
+// Copyright (C) 2021 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+esid: sec-temporal.now.instant
+description: Temporal.now.instant.name is "instant".
+includes: [propertyHelper.js]
+features: [Temporal]
+---*/
+
+assert.sameValue(Temporal.now.instant.name, 'instant');
+
+verifyProperty(Temporal.now.instant, 'name', {
+  enumerable: false,
+  writable: false,
+  configurable: true
+});

test/built-ins/Temporal/now/instant/not-a-constructor.js

@@ -0,0 +1,14 @@
+// Copyright (C) 2021 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+esid: sec-temporal.now.instant
+description: Temporal.now.instant does not implement [[Construct]]
+includes: [isConstructor.js]
+features: [Reflect.construct, Temporal]
+---*/
+
+assert.sameValue(isConstructor(Temporal.now.instant), false, 'isConstructor(Temporal.now.instant) must return false');
+
+assert.throws(TypeError, () => {
+  new Temporal.now.instant();
+}, '`new Temporal.now.instant()` throws TypeError');

test/built-ins/Temporal/now/instant/prop-desc.js

@@ -0,0 +1,14 @@
+// Copyright (C) 2021 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+esid: sec-temporal.now.instant
+description: The "instant" property of Temporal.now
+includes: [propertyHelper.js]
+features: [Temporal]
+---*/
+
+verifyProperty(Temporal.now, 'instant', {
+  enumerable: false,
+  writable: true,
+  configurable: true
+});

test/built-ins/Temporal/now/instant/return-value-distinct.js

@@ -0,0 +1,12 @@
+// Copyright (C) 2021 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+esid: sec-temporal.now.instant
+description: Each invocation of the function produces a distinct object value
+features: [Temporal]
+---*/
+
+var instant1 = Temporal.now.instant();
+var instant2 = Temporal.now.instant();
+
+assert.notSameValue(instant1, instant2);

test/built-ins/Temporal/now/instant/return-value-prototype.js

@@ -0,0 +1,12 @@
+// Copyright (C) 2021 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+esid: sec-temporal.now.instant
+description: Temporal.now.instant returns an instance of the Instant constructor
+features: [Temporal]
+---*/
+
+assert.sameValue(
+  Object.getPrototypeOf(Temporal.now.instant()),
+  Temporal.Instant.prototype
+);

test/built-ins/Temporal/now/instant/return-value-value.js

@@ -0,0 +1,16 @@
+// Copyright (C) 2021 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+esid: sec-temporal.now.instant
+description: >
+  Temporal.now.instant returns an Instant describing the current moment in time
+  (as corroborated by `Date.now`)
+features: [Temporal, BigInt]
+---*/
+
+var nowBefore = Date.now();
+var seconds = Number(Temporal.now.instant().epochNanoseconds / 1000000n);
+var nowAfter = Date.now();
+
+assert(seconds >= nowBefore, 'before');
+assert(seconds <= nowAfter, 'after');