diff --git a/harness/temporalHelpers.js b/harness/temporalHelpers.js
index a3579b0b78..09ba11c9fc 100644
--- a/harness/temporalHelpers.js
+++ b/harness/temporalHelpers.js
@@ -28,6 +28,29 @@ var TemporalHelpers = {
     assert.sameValue(duration.nanoseconds, nanoseconds, `${description} nanoseconds result`);
   },
 
+  /*
+   * assertDurationsEqual(actual, expected[, description]):
+   *
+   * Shorthand for asserting that each field of a Temporal.Duration is equal to
+   * the corresponding field in another Temporal.Duration.
+   */
+  assertDurationsEqual(actual, expected, description = "") {
+    assert(expected instanceof Temporal.Duration, `${description} expected value should be a Temporal.Duration`);
+    TemporalHelpers.assertDuration(actual, expected.years, expected.months, expected.weeks, expected.days, expected.hours, expected.minutes, expected.seconds, expected.milliseconds, expected.microseconds, expected.nanoseconds, description);
+  },
+
+  /*
+   * assertInstantsEqual(actual, expected[, description]):
+   *
+   * Shorthand for asserting that two Temporal.Instants are of the correct type
+   * and equal according to their equals() methods.
+   */
+  assertInstantsEqual(actual, expected, description = "") {
+    assert(expected instanceof Temporal.Instant, `${description} expected value should be a Temporal.Instant`);
+    assert(actual instanceof Temporal.Instant, `${description} instanceof`);
+    assert(actual.equals(expected), `${description} equals method`);
+  },
+
   /*
    * assertPlainDate(date, year, ..., nanosecond[, description[, era, eraYear]]):
    *
@@ -70,6 +93,20 @@ var TemporalHelpers = {
     assert.sameValue(datetime.nanosecond, nanosecond, `${description} nanosecond result`);
   },
 
+  /*
+   * assertPlainDateTimesEqual(actual, expected[, description]):
+   *
+   * Shorthand for asserting that two Temporal.PlainDateTimes are of the correct
+   * type, equal according to their equals() methods, and additionally that
+   * their calendars are the same value.
+   */
+  assertPlainDateTimesEqual(actual, expected, description = "") {
+    assert(expected instanceof Temporal.PlainDateTime, `${description} expected value should be a Temporal.PlainDateTime`);
+    assert(actual instanceof Temporal.PlainDateTime, `${description} instanceof`);
+    assert(actual.equals(expected), `${description} equals method`);
+    assert.sameValue(actual.calendar, expected.calendar, `${description} calendar same value`);
+  },
+
   /*
    * assertPlainMonthDay(monthDay, monthCode, day[, description [, referenceISOYear]]):
    *
@@ -101,6 +138,18 @@ var TemporalHelpers = {
     assert.sameValue(time.nanosecond, nanosecond, `${description} nanosecond result`);
   },
 
+  /*
+   * assertPlainTimesEqual(actual, expected[, description]):
+   *
+   * Shorthand for asserting that two Temporal.PlainTimes are of the correct
+   * type and equal according to their equals() methods.
+   */
+  assertPlainTimesEqual(actual, expected, description = "") {
+    assert(expected instanceof Temporal.PlainTime, `${description} expected value should be a Temporal.PlainTime`);
+    assert(actual instanceof Temporal.PlainTime, `${description} instanceof`);
+    assert(actual.equals(expected), `${description} equals method`);
+  },
+
   /*
    * assertPlainYearMonth(yearMonth, year, month, monthCode[, description[, era, eraYear]]):
    *
@@ -118,6 +167,21 @@ var TemporalHelpers = {
     assert.sameValue(yearMonth.monthCode, monthCode, `${description} monthCode result`);
   },
 
+  /*
+   * assertZonedDateTimesEqual(actual, expected[, description]):
+   *
+   * Shorthand for asserting that two Temporal.ZonedDateTimes are of the correct
+   * type, equal according to their equals() methods, and additionally that
+   * their time zones and calendars are the same value.
+   */
+  assertZonedDateTimesEqual(actual, expected, description = "") {
+    assert(expected instanceof Temporal.ZonedDateTime, `${description} expected value should be a Temporal.ZonedDateTime`);
+    assert(actual instanceof Temporal.ZonedDateTime, `${description} instanceof`);
+    assert(actual.equals(expected), `${description} equals method`);
+    assert.sameValue(actual.timeZone, expected.timeZone, `${description} time zone same value`);
+    assert.sameValue(actual.calendar, expected.calendar, `${description} calendar same value`);
+  },
+
   /*
    * assertUnreachable(description):
    *
@@ -282,24 +346,17 @@ var TemporalHelpers = {
     validSingularUnits.forEach((unit) => {
       const singularValue = func(unit);
       const pluralValue = func(plurals[unit]);
+      const desc = `Plural ${plurals[unit]} produces the same result as singular ${unit}`;
       if (singularValue instanceof Temporal.Duration) {
-        assert.sameValue(pluralValue.years, singularValue.years, "years value");
-        assert.sameValue(pluralValue.months, singularValue.months, "months value");
-        assert.sameValue(pluralValue.weeks, singularValue.weeks, "weeks value");
-        assert.sameValue(pluralValue.days, singularValue.days, "days value");
-        assert.sameValue(pluralValue.hours, singularValue.hours, "hours value");
-        assert.sameValue(pluralValue.minutes, singularValue.minutes, "minutes value");
-        assert.sameValue(pluralValue.seconds, singularValue.seconds, "seconds value");
-        assert.sameValue(pluralValue.milliseconds, singularValue.milliseconds, "milliseconds value");
-        assert.sameValue(pluralValue.microseconds, singularValue.microseconds, "microseconds value");
-        assert.sameValue(pluralValue.nanoseconds, singularValue.nanoseconds, "nanoseconds value");
-      } else if (
-        singularValue instanceof Temporal.Instant ||
-        singularValue instanceof Temporal.PlainDateTime ||
-        singularValue instanceof Temporal.PlainTime ||
-        singularValue instanceof Temporal.ZonedDateTime
-      ) {
-        assert(pluralValue.equals(singularValue), "Temporal objects equal");
+        TemporalHelpers.assertDurationsEqual(pluralValue, singularValue, desc);
+      } else if (singularValue instanceof Temporal.Instant) {
+        TemporalHelpers.assertInstantsEqual(pluralValue, singularValue, desc);
+      } else if (singularValue instanceof Temporal.PlainDateTime) {
+        TemporalHelpers.assertPlainDateTimesEqual(pluralValue, singularValue, desc);
+      } else if (singularValue instanceof Temporal.PlainTime) {
+        TemporalHelpers.assertPlainTimesEqual(pluralValue, singularValue, desc);
+      } else if (singularValue instanceof Temporal.ZonedDateTime) {
+        TemporalHelpers.assertZonedDateTimesEqual(pluralValue, singularValue, desc);
       } else {
         assert.sameValue(pluralValue, singularValue);
       }
diff --git a/test/built-ins/Temporal/Duration/prototype/round/smallestunit-disallowed-units-string.js b/test/built-ins/Temporal/Duration/prototype/round/smallestunit-disallowed-units-string.js
new file mode 100644
index 0000000000..f2cf0b0f01
--- /dev/null
+++ b/test/built-ins/Temporal/Duration/prototype/round/smallestunit-disallowed-units-string.js
@@ -0,0 +1,26 @@
+// Copyright (C) 2021 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.duration.prototype.round
+description: Specifically disallowed units for the smallestUnit option
+features: [Temporal, arrow-function]
+---*/
+
+const instance = new Temporal.Duration(0, 0, 0, 4, 5, 6, 7, 987, 654, 321);
+const invalidUnits = [
+  "era",
+  "eras",
+];
+invalidUnits.forEach((smallestUnit) => {
+  assert.throws(
+    RangeError,
+    () => instance.round({ smallestUnit }),
+    `{ smallestUnit: "${smallestUnit}" } should not be allowed as an argument to round`
+  );
+  assert.throws(
+    RangeError,
+    () => instance.round(smallestUnit),
+    `"${smallestUnit}" should not be allowed as an argument to round`
+  );
+});
diff --git a/test/built-ins/Temporal/Duration/prototype/round/smallestunit-plurals-accepted-string.js b/test/built-ins/Temporal/Duration/prototype/round/smallestunit-plurals-accepted-string.js
new file mode 100644
index 0000000000..d5e4c6dd41
--- /dev/null
+++ b/test/built-ins/Temporal/Duration/prototype/round/smallestunit-plurals-accepted-string.js
@@ -0,0 +1,21 @@
+// Copyright (C) 2021 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.duration.prototype.round
+description: Plural units are accepted as well for the shorthand for the smallestUnit option
+includes: [temporalHelpers.js]
+features: [Temporal, arrow-function]
+---*/
+
+const duration = new Temporal.Duration(0, 0, 0, 4, 5, 6, 7, 987, 654, 321);
+const validUnits = [
+  "day",
+  "hour",
+  "minute",
+  "second",
+  "millisecond",
+  "microsecond",
+  "nanosecond",
+];
+TemporalHelpers.checkPluralUnitsAccepted((smallestUnit) => duration.round(smallestUnit), validUnits);
diff --git a/test/built-ins/Temporal/Duration/prototype/round/smallestunit-string-shorthand-string.js b/test/built-ins/Temporal/Duration/prototype/round/smallestunit-string-shorthand-string.js
new file mode 100644
index 0000000000..1fe8cf56a5
--- /dev/null
+++ b/test/built-ins/Temporal/Duration/prototype/round/smallestunit-string-shorthand-string.js
@@ -0,0 +1,25 @@
+// Copyright (C) 2021 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.duration.prototype.round
+description: String as first argument is equivalent to options bag with smallestUnit option
+includes: [temporalHelpers.js]
+features: [Temporal, arrow-function]
+---*/
+
+const instance = new Temporal.Duration(0, 0, 0, 4, 5, 6, 7, 987, 654, 321);
+const validUnits = [
+  "day",
+  "hour",
+  "minute",
+  "second",
+  "millisecond",
+  "microsecond",
+  "nanosecond",
+];
+validUnits.forEach((smallestUnit) => {
+  const full = instance.round({ smallestUnit });
+  const shorthand = instance.round(smallestUnit);
+  TemporalHelpers.assertDurationsEqual(shorthand, full, `"${smallestUnit}" as first argument to round is equivalent to options bag`);
+});
diff --git a/test/built-ins/Temporal/Duration/prototype/total/options-wrong-type.js b/test/built-ins/Temporal/Duration/prototype/total/options-wrong-type.js
index 671a9d7319..9b92bca483 100644
--- a/test/built-ins/Temporal/Duration/prototype/total/options-wrong-type.js
+++ b/test/built-ins/Temporal/Duration/prototype/total/options-wrong-type.js
@@ -11,7 +11,6 @@ const values = [
   undefined,
   null,
   true,
-  "string",
   Symbol(),
   1,
   2n,
diff --git a/test/built-ins/Temporal/Duration/prototype/total/relativeto-undefined-throw-on-calendar-units.js b/test/built-ins/Temporal/Duration/prototype/total/relativeto-undefined-throw-on-calendar-units.js
index 7014f4fcde..e89953a724 100644
--- a/test/built-ins/Temporal/Duration/prototype/total/relativeto-undefined-throw-on-calendar-units.js
+++ b/test/built-ins/Temporal/Duration/prototype/total/relativeto-undefined-throw-on-calendar-units.js
@@ -5,8 +5,8 @@
 esid: sec-temporal.duration.prototype.total
 description: >
     The relativeTo option is required when the Duration contains years, months,
-    or weeks, and largestUnit is days; or largestUnit is weeks or months
-features: [Temporal]
+    or weeks, and unit is days; or unit is weeks or months
+features: [Temporal, arrow-function]
 ---*/
 
 const oneYear = new Temporal.Duration(1);
@@ -16,12 +16,17 @@ const oneDay = new Temporal.Duration(0, 0, 0, 1);
 
 const options = { unit: "days" };
 assert.sameValue(oneDay.total(options), 1, "days do not require relativeTo");
+assert.sameValue(oneDay.total("days"), 1, "days do not require relativeTo (string shorthand)");
 assert.throws(RangeError, () => oneWeek.total(options), "total days of weeks requires relativeTo");
+assert.throws(RangeError, () => oneWeek.total("days"), "total days of weeks requires relativeTo (string shorthand)");
 assert.throws(RangeError, () => oneMonth.total(options), "total days of months requires relativeTo");
+assert.throws(RangeError, () => oneMonth.total("days"), "total days of months requires relativeTo (string shorthand)");
 assert.throws(RangeError, () => oneYear.total(options), "total days of years requires relativeTo");
+assert.throws(RangeError, () => oneYear.total("days"), "total days of years requires relativeTo (string shorthand)");
 
 ["months", "weeks"].forEach((unit) => {
   [oneDay, oneWeek, oneMonth, oneYear].forEach((duration) => {
     assert.throws(RangeError, () => duration.total({ unit }), `${duration} total ${unit} requires relativeTo`);
+    assert.throws(RangeError, () => duration.total(unit), `${duration} total ${unit} requires relativeTo (string shorthand)`);
   });
 });
diff --git a/test/built-ins/Temporal/Duration/prototype/total/unit-disallowed-units-string.js b/test/built-ins/Temporal/Duration/prototype/total/unit-disallowed-units-string.js
new file mode 100644
index 0000000000..6d708f54db
--- /dev/null
+++ b/test/built-ins/Temporal/Duration/prototype/total/unit-disallowed-units-string.js
@@ -0,0 +1,26 @@
+// Copyright (C) 2021 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.duration.prototype.total
+description: Specifically disallowed units for the unit option
+features: [Temporal, arrow-function]
+---*/
+
+const instance = new Temporal.Duration(0, 0, 0, 4, 5, 6, 7, 987, 654, 321);
+const invalidUnits = [
+  "era",
+  "eras",
+];
+invalidUnits.forEach((unit) => {
+  assert.throws(
+    RangeError,
+    () => instance.total({ unit }),
+    `{ unit: "${unit}" } should not be allowed as an argument to total`
+  );
+  assert.throws(
+    RangeError,
+    () => instance.total(unit),
+    `"${unit}" should not be allowed as an argument to total`
+  );
+});
diff --git a/test/built-ins/Temporal/Duration/prototype/total/unit-plurals-accepted-string.js b/test/built-ins/Temporal/Duration/prototype/total/unit-plurals-accepted-string.js
new file mode 100644
index 0000000000..5cf954bf52
--- /dev/null
+++ b/test/built-ins/Temporal/Duration/prototype/total/unit-plurals-accepted-string.js
@@ -0,0 +1,21 @@
+// Copyright (C) 2021 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.duration.prototype.total
+description: Plural units are accepted as well for the shorthand for the unit option
+includes: [temporalHelpers.js]
+features: [Temporal, arrow-function]
+---*/
+
+const duration = new Temporal.Duration(0, 0, 0, 4, 5, 6, 7, 987, 654, 321);
+const validUnits = [
+  "day",
+  "hour",
+  "minute",
+  "second",
+  "millisecond",
+  "microsecond",
+  "nanosecond",
+];
+TemporalHelpers.checkPluralUnitsAccepted((unit) => duration.total(unit), validUnits);
diff --git a/test/built-ins/Temporal/Duration/prototype/total/unit-string-shorthand-string.js b/test/built-ins/Temporal/Duration/prototype/total/unit-string-shorthand-string.js
new file mode 100644
index 0000000000..1b90e01fb7
--- /dev/null
+++ b/test/built-ins/Temporal/Duration/prototype/total/unit-string-shorthand-string.js
@@ -0,0 +1,24 @@
+// Copyright (C) 2021 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.duration.prototype.total
+description: String as first argument is equivalent to options bag with unit option
+features: [Temporal, arrow-function]
+---*/
+
+const instance = new Temporal.Duration(0, 0, 0, 4, 5, 6, 7, 987, 654, 321);
+const validUnits = [
+  "day",
+  "hour",
+  "minute",
+  "second",
+  "millisecond",
+  "microsecond",
+  "nanosecond",
+];
+validUnits.forEach((unit) => {
+  const full = instance.total({ unit });
+  const shorthand = instance.total(unit);
+  assert.sameValue(shorthand, full, `"${unit}" as first argument to total is equivalent to options bag`);
+});
diff --git a/test/built-ins/Temporal/Instant/prototype/round/options-wrong-type.js b/test/built-ins/Temporal/Instant/prototype/round/options-wrong-type.js
index 455401e261..51cba2ff1a 100644
--- a/test/built-ins/Temporal/Instant/prototype/round/options-wrong-type.js
+++ b/test/built-ins/Temporal/Instant/prototype/round/options-wrong-type.js
@@ -11,7 +11,6 @@ const values = [
   undefined,
   null,
   true,
-  "string",
   Symbol(),
   1,
   2n,
diff --git a/test/built-ins/Temporal/Instant/prototype/round/smallestunit-disallowed-units.js b/test/built-ins/Temporal/Instant/prototype/round/smallestunit-disallowed-units.js
new file mode 100644
index 0000000000..2d7dcb1d5f
--- /dev/null
+++ b/test/built-ins/Temporal/Instant/prototype/round/smallestunit-disallowed-units.js
@@ -0,0 +1,34 @@
+// Copyright (C) 2021 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.instant.prototype.round
+description: Specifically disallowed units for the smallestUnit option
+features: [Temporal, arrow-function]
+---*/
+
+const instance = new Temporal.Instant(1_000_000_000_987_654_321n);
+const invalidUnits = [
+  "era",
+  "eras",
+  "year",
+  "month",
+  "week",
+  "years",
+  "months",
+  "weeks",
+  "day",
+  "days",
+];
+invalidUnits.forEach((smallestUnit) => {
+  assert.throws(
+    RangeError,
+    () => instance.round({ smallestUnit }),
+    `{ smallestUnit: "${smallestUnit}" } should not be allowed as an argument to round`
+  );
+  assert.throws(
+    RangeError,
+    () => instance.round(smallestUnit),
+    `"${smallestUnit}" should not be allowed as an argument to round`
+  );
+});
diff --git a/test/built-ins/Temporal/Instant/prototype/round/smallestunit-plurals-accepted.js b/test/built-ins/Temporal/Instant/prototype/round/smallestunit-plurals-accepted.js
index 67765e46c1..6db2285846 100644
--- a/test/built-ins/Temporal/Instant/prototype/round/smallestunit-plurals-accepted.js
+++ b/test/built-ins/Temporal/Instant/prototype/round/smallestunit-plurals-accepted.js
@@ -5,7 +5,7 @@
 esid: sec-temporal.instant.prototype.round
 description: Plural units are accepted as well for the smallestUnit option
 includes: [temporalHelpers.js]
-features: [Temporal]
+features: [Temporal, arrow-function]
 ---*/
 
 const instant = new Temporal.Instant(1_000_000_000_987_654_321n);
@@ -18,3 +18,4 @@ const validUnits = [
   "nanosecond",
 ];
 TemporalHelpers.checkPluralUnitsAccepted((smallestUnit) => instant.round({ smallestUnit }), validUnits);
+TemporalHelpers.checkPluralUnitsAccepted((smallestUnit) => instant.round(smallestUnit), validUnits);
diff --git a/test/built-ins/Temporal/Instant/prototype/round/smallestunit-string-shorthand.js b/test/built-ins/Temporal/Instant/prototype/round/smallestunit-string-shorthand.js
new file mode 100644
index 0000000000..dd520d27b4
--- /dev/null
+++ b/test/built-ins/Temporal/Instant/prototype/round/smallestunit-string-shorthand.js
@@ -0,0 +1,24 @@
+// Copyright (C) 2021 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.instant.prototype.round
+description: String as first argument is equivalent to options bag with smallestUnit option
+includes: [temporalHelpers.js]
+features: [Temporal, arrow-function]
+---*/
+
+const instance = new Temporal.Instant(1_000_000_000_987_654_321n);
+const validUnits = [
+  "hour",
+  "minute",
+  "second",
+  "millisecond",
+  "microsecond",
+  "nanosecond",
+];
+validUnits.forEach((smallestUnit) => {
+  const full = instance.round({ smallestUnit });
+  const shorthand = instance.round(smallestUnit);
+  TemporalHelpers.assertInstantsEqual(shorthand, full, `"${smallestUnit}" as first argument to round is equivalent to options bag`);
+});
diff --git a/test/built-ins/Temporal/PlainDateTime/prototype/round/smallestunit-disallowed-units.js b/test/built-ins/Temporal/PlainDateTime/prototype/round/smallestunit-disallowed-units.js
new file mode 100644
index 0000000000..cd85d00ae1
--- /dev/null
+++ b/test/built-ins/Temporal/PlainDateTime/prototype/round/smallestunit-disallowed-units.js
@@ -0,0 +1,32 @@
+// Copyright (C) 2021 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindatetime.prototype.round
+description: Specifically disallowed units for the smallestUnit option
+features: [Temporal, arrow-function]
+---*/
+
+const instance = new Temporal.PlainDateTime(2000, 5, 2, 12, 34, 56, 789, 999, 999);
+const invalidUnits = [
+  "era",
+  "eras",
+  "year",
+  "month",
+  "week",
+  "years",
+  "months",
+  "weeks",
+];
+invalidUnits.forEach((smallestUnit) => {
+  assert.throws(
+    RangeError,
+    () => instance.round({ smallestUnit }),
+    `{ smallestUnit: "${smallestUnit}" } should not be allowed as an argument to round`
+  );
+  assert.throws(
+    RangeError,
+    () => instance.round(smallestUnit),
+    `"${smallestUnit}" should not be allowed as an argument to round`
+  );
+});
diff --git a/test/built-ins/Temporal/PlainDateTime/prototype/round/smallestunit-plurals-accepted.js b/test/built-ins/Temporal/PlainDateTime/prototype/round/smallestunit-plurals-accepted.js
index c80362d92d..0868af0c88 100644
--- a/test/built-ins/Temporal/PlainDateTime/prototype/round/smallestunit-plurals-accepted.js
+++ b/test/built-ins/Temporal/PlainDateTime/prototype/round/smallestunit-plurals-accepted.js
@@ -5,7 +5,7 @@
 esid: sec-temporal.plaindatetime.prototype.round
 description: Plural units are accepted as well for the smallestUnit option
 includes: [temporalHelpers.js]
-features: [Temporal]
+features: [Temporal, arrow-function]
 ---*/
 
 const datetime = new Temporal.PlainDateTime(2000, 5, 2, 12, 34, 56, 789, 999, 999);
@@ -19,3 +19,4 @@ const validUnits = [
   "nanosecond",
 ];
 TemporalHelpers.checkPluralUnitsAccepted((smallestUnit) => datetime.round({ smallestUnit }), validUnits);
+TemporalHelpers.checkPluralUnitsAccepted((smallestUnit) => datetime.round(smallestUnit), validUnits);
diff --git a/test/built-ins/Temporal/PlainDateTime/prototype/round/smallestunit-string-shorthand.js b/test/built-ins/Temporal/PlainDateTime/prototype/round/smallestunit-string-shorthand.js
new file mode 100644
index 0000000000..a8bda1980c
--- /dev/null
+++ b/test/built-ins/Temporal/PlainDateTime/prototype/round/smallestunit-string-shorthand.js
@@ -0,0 +1,25 @@
+// Copyright (C) 2021 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindatetime.prototype.round
+description: String as first argument is equivalent to options bag with smallestUnit option
+includes: [temporalHelpers.js]
+features: [Temporal, arrow-function]
+---*/
+
+const instance = new Temporal.PlainDateTime(2000, 5, 2, 12, 34, 56, 789, 999, 999);
+const validUnits = [
+  "day",
+  "hour",
+  "minute",
+  "second",
+  "millisecond",
+  "microsecond",
+  "nanosecond",
+];
+validUnits.forEach((smallestUnit) => {
+  const full = instance.round({ smallestUnit });
+  const shorthand = instance.round(smallestUnit);
+  TemporalHelpers.assertPlainDateTimesEqual(shorthand, full, `"${smallestUnit}" as first argument to round is equivalent to options bag`);
+});
diff --git a/test/built-ins/Temporal/PlainTime/prototype/round/smallestunit-disallowed-units.js b/test/built-ins/Temporal/PlainTime/prototype/round/smallestunit-disallowed-units.js
new file mode 100644
index 0000000000..1a9da4e74a
--- /dev/null
+++ b/test/built-ins/Temporal/PlainTime/prototype/round/smallestunit-disallowed-units.js
@@ -0,0 +1,34 @@
+// Copyright (C) 2021 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaintime.prototype.round
+description: Specifically disallowed units for the smallestUnit option
+features: [Temporal, arrow-function]
+---*/
+
+const instance = new Temporal.PlainTime(12, 34, 56, 789, 999, 999);
+const invalidUnits = [
+  "era",
+  "eras",
+  "year",
+  "month",
+  "week",
+  "years",
+  "months",
+  "weeks",
+  "day",
+  "days",
+];
+invalidUnits.forEach((smallestUnit) => {
+  assert.throws(
+    RangeError,
+    () => instance.round({ smallestUnit }),
+    `{ smallestUnit: "${smallestUnit}" } should not be allowed as an argument to round`
+  );
+  assert.throws(
+    RangeError,
+    () => instance.round(smallestUnit),
+    `"${smallestUnit}" should not be allowed as an argument to round`
+  );
+});
diff --git a/test/built-ins/Temporal/PlainTime/prototype/round/smallestunit-plurals-accepted.js b/test/built-ins/Temporal/PlainTime/prototype/round/smallestunit-plurals-accepted.js
index 32ab2bbfee..d903c8ede1 100644
--- a/test/built-ins/Temporal/PlainTime/prototype/round/smallestunit-plurals-accepted.js
+++ b/test/built-ins/Temporal/PlainTime/prototype/round/smallestunit-plurals-accepted.js
@@ -5,7 +5,7 @@
 esid: sec-temporal.plaintime.prototype.round
 description: Plural units are accepted as well for the smallestUnit option
 includes: [temporalHelpers.js]
-features: [Temporal]
+features: [Temporal, arrow-function]
 ---*/
 
 const time = new Temporal.PlainTime(12, 34, 56, 789, 999, 999);
@@ -18,3 +18,4 @@ const validUnits = [
   "nanosecond",
 ];
 TemporalHelpers.checkPluralUnitsAccepted((smallestUnit) => time.round({ smallestUnit }), validUnits);
+TemporalHelpers.checkPluralUnitsAccepted((smallestUnit) => time.round(smallestUnit), validUnits);
diff --git a/test/built-ins/Temporal/PlainTime/prototype/round/smallestunit-string-shorthand.js b/test/built-ins/Temporal/PlainTime/prototype/round/smallestunit-string-shorthand.js
new file mode 100644
index 0000000000..0dc103e30d
--- /dev/null
+++ b/test/built-ins/Temporal/PlainTime/prototype/round/smallestunit-string-shorthand.js
@@ -0,0 +1,24 @@
+// Copyright (C) 2021 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaintime.prototype.round
+description: String as first argument is equivalent to options bag with smallestUnit option
+includes: [temporalHelpers.js]
+features: [Temporal, arrow-function]
+---*/
+
+const instance = new Temporal.PlainTime(12, 34, 56, 789, 999, 999);
+const validUnits = [
+  "hour",
+  "minute",
+  "second",
+  "millisecond",
+  "microsecond",
+  "nanosecond",
+];
+validUnits.forEach((smallestUnit) => {
+  const full = instance.round({ smallestUnit });
+  const shorthand = instance.round(smallestUnit);
+  TemporalHelpers.assertPlainTimesEqual(shorthand, full, `"${smallestUnit}" as first argument to round is equivalent to options bag`);
+});
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/round/smallestunit-disallowed-units.js b/test/built-ins/Temporal/ZonedDateTime/prototype/round/smallestunit-disallowed-units.js
new file mode 100644
index 0000000000..f89f4c6752
--- /dev/null
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/round/smallestunit-disallowed-units.js
@@ -0,0 +1,32 @@
+// Copyright (C) 2021 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.zoneddatetime.prototype.round
+description: Specifically disallowed units for the smallestUnit option
+features: [Temporal, arrow-function]
+---*/
+
+const instance = new Temporal.ZonedDateTime(1_000_000_000_987_654_321n, "UTC");
+const invalidUnits = [
+  "era",
+  "eras",
+  "year",
+  "month",
+  "week",
+  "years",
+  "months",
+  "weeks",
+];
+invalidUnits.forEach((smallestUnit) => {
+  assert.throws(
+    RangeError,
+    () => instance.round({ smallestUnit }),
+    `{ smallestUnit: "${smallestUnit}" } should not be allowed as an argument to round`
+  );
+  assert.throws(
+    RangeError,
+    () => instance.round(smallestUnit),
+    `"${smallestUnit}" should not be allowed as an argument to round`
+  );
+});
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/round/smallestunit-plurals-accepted.js b/test/built-ins/Temporal/ZonedDateTime/prototype/round/smallestunit-plurals-accepted.js
index 2ffe1ec676..b4c85a10e4 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/round/smallestunit-plurals-accepted.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/round/smallestunit-plurals-accepted.js
@@ -5,7 +5,7 @@
 esid: sec-temporal.zoneddatetime.prototype.round
 description: Plural units are accepted as well for the smallestUnit option
 includes: [temporalHelpers.js]
-features: [Temporal]
+features: [Temporal, arrow-function]
 ---*/
 
 const datetime = new Temporal.ZonedDateTime(1_000_000_000_987_654_321n, "UTC");
@@ -19,3 +19,4 @@ const validUnits = [
   "nanosecond",
 ];
 TemporalHelpers.checkPluralUnitsAccepted((smallestUnit) => datetime.round({ smallestUnit }), validUnits);
+TemporalHelpers.checkPluralUnitsAccepted((smallestUnit) => datetime.round(smallestUnit), validUnits);
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/round/smallestunit-string-shorthand.js b/test/built-ins/Temporal/ZonedDateTime/prototype/round/smallestunit-string-shorthand.js
new file mode 100644
index 0000000000..fdc34c59f7
--- /dev/null
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/round/smallestunit-string-shorthand.js
@@ -0,0 +1,25 @@
+// Copyright (C) 2021 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.zoneddatetime.prototype.round
+description: String as first argument is equivalent to options bag with smallestUnit option
+includes: [temporalHelpers.js]
+features: [Temporal, arrow-function]
+---*/
+
+const instance = new Temporal.ZonedDateTime(1_000_000_000_987_654_321n, "UTC");
+const validUnits = [
+  "day",
+  "hour",
+  "minute",
+  "second",
+  "millisecond",
+  "microsecond",
+  "nanosecond",
+];
+validUnits.forEach((smallestUnit) => {
+  const full = instance.round({ smallestUnit });
+  const shorthand = instance.round(smallestUnit);
+  TemporalHelpers.assertZonedDateTimesEqual(shorthand, full, `"${smallestUnit}" as first argument to round is equivalent to options bag`);
+});