Add tests for Intl.DateTimeFormat formatRange(ToParts) to check the b…

…ehavior when startDate is the same as endDate (tc39/proposal-intl-DateTimeFormat-formatRange#19).

test/intl402/DateTimeFormat/prototype/formatRange/date-same-returns-single-date.js

@@ -0,0 +1,42 @@
+// Copyright 2019 Google Inc. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-partitiondatetimerangepattern
+description: >
+  When startDate is equal to endDate, the output should be a string equal
+  to the output of Intl.DateTimeFormat.prototype.format.
+info: |
+  Intl.DateTimeFormat.prototype.formatRange ( startDate , endDate )
+  
+  4. Let x be ? ToNumber(startDate).
+  5. Let y be ? ToNumber(endDate).
+  6. Return ? FormatDateTimeRange(dtf, x, y).
+
+  PartitionDateTimeRangePattern ( dateTimeFormat, x, y )
+
+  13. If dateFieldsPracticallyEqual is true, then
+    a. Let pattern be dateTimeFormat.[[Pattern]].
+    b. Let patternParts be PartitionPattern(pattern).
+    c. Let result be ? FormatDateTimePattern(dateTimeFormat, patternParts, tm1).
+    d. For each r in result do
+      i. Set r.[[Source]] to "shared".
+    e. Return result.
+
+features: [Intl.DateTimeFormat-formatRange]
+locale: [en-US]
+---*/
+
+const date = new Date(2019, 7, 10,  1, 2, 3, 234);
+
+let dtf = new Intl.DateTimeFormat("en", { year: "numeric", month: "short", day: "numeric" });
+assert.sameValue(dtf.formatRange(date, date), dtf.format(date), "same output with date options");
+
+dtf = new Intl.DateTimeFormat("en", { minute: "numeric", second: "numeric" });
+assert.sameValue(dtf.formatRange(date, date), dtf.format(date), "same output with time options");
+
+dtf = new Intl.DateTimeFormat("en", { month: "short", day: "numeric", minute: "numeric" });
+assert.sameValue(dtf.formatRange(date, date), dtf.format(date), "same output with date-time options");
+
+dtf = new Intl.DateTimeFormat("en", { dateStyle: "long", timeStyle: "short" });
+assert.sameValue(dtf.formatRange(date, date), dtf.format(date), "same output with dateStyle/timeStyle");

test/intl402/DateTimeFormat/prototype/formatRangeToParts/date-same-returns-single-date.js

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+// Copyright 2019 Google Inc. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-partitiondatetimerangepattern
+description: >
+  When startDate is equal to endDate, the output should be an Array of objects with the
+  same value for the `type` and `value` fields as in the Array returned by
+  Intl.DateTimeFormat.prototype.formatToParts.
+info: |
+  Intl.DateTimeFormat.prototype.formatRangeToParts ( startDate , endDate )
+  
+  4. Let x be ? ToNumber(startDate).
+  5. Let y be ? ToNumber(endDate).
+  6. Return ? FormatDateTimeRange(dtf, x, y).
+
+  PartitionDateTimeRangePattern ( dateTimeFormat, x, y )
+
+  13. If dateFieldsPracticallyEqual is true, then
+    a. Let pattern be dateTimeFormat.[[Pattern]].
+    b. Let patternParts be PartitionPattern(pattern).
+    c. Let result be ? FormatDateTimePattern(dateTimeFormat, patternParts, tm1).
+    d. For each r in result do
+      i. Set r.[[Source]] to "shared".
+    e. Return result.
+
+features: [Intl.DateTimeFormat-formatRange]
+locale: [en-US]
+---*/
+
+function* zip(a, b) {
+  assert.sameValue(a.length, b.length);
+  for (let i = 0; i < a.length; ++i) {
+    yield [i, a[i], b[i]];
+  }
+}
+
+function compare(actual, expected) {
+  for (const [i, actualEntry, expectedEntry] of zip(actual, expected)) {
+    assert.sameValue(actualEntry.type, expectedEntry.type, `type for entry ${i}`);
+    assert.sameValue(actualEntry.value, expectedEntry.value, `value for entry ${i}`);
+  }
+}
+
+const date = new Date(2019, 7, 10,  1, 2, 3, 234);
+
+let dtf = new Intl.DateTimeFormat("en", { year: "numeric", month: "short", day: "numeric" });
+compare(dtf.formatRange(date, date), dtf.format(date), "same output with date options");
+
+dtf = new Intl.DateTimeFormat("en", { minute: "numeric", second: "numeric" });
+compare(dtf.formatRange(date, date), dtf.format(date), "same output with time options");
+
+dtf = new Intl.DateTimeFormat("en", { month: "short", day: "numeric", minute: "numeric" });
+compare(dtf.formatRange(date, date), dtf.format(date), "same output with date-time options");
+
+dtf = new Intl.DateTimeFormat("en", { dateStyle: "long", timeStyle: "short" });
+compare(dtf.formatRange(date, date), dtf.format(date), "same output with dateStyle/timeStyle");