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Add test coverage for DateTime.ParseExact with different DateTimeStyles #123600

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Merged
stephentoub merged 3 commits into from
Jan 26, 2026
Merged

Add test coverage for DateTime.ParseExact with different DateTimeStyles #123600

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96aaf6c
Initial plan
Copilot Jan 25, 2026
c380d0a
Add test coverage for DateTime.ParseExact with different DateTimeStyles
Copilot Jan 25, 2026
cea601d
Simplify format strings per code review feedback
Copilot Jan 25, 2026
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26 changes: 23 additions & 3 deletions src/libraries/System.Runtime/tests/System.Runtime.Tests/System/DateTimeTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -1994,13 +1994,16 @@ public object GetFormat(Type formatType)
}
}

[Fact]
public static void InvalidDateTimeStyles()
[Theory]
[InlineData(DateTimeStyles.AssumeLocal | DateTimeStyles.AssumeUniversal)]
[InlineData(DateTimeStyles.RoundtripKind | DateTimeStyles.AssumeLocal)]
[InlineData(DateTimeStyles.RoundtripKind | DateTimeStyles.AssumeUniversal)]
[InlineData(DateTimeStyles.RoundtripKind | DateTimeStyles.AdjustToUniversal)]
public static void InvalidDateTimeStyles(DateTimeStyles style)
{
string strDateTime = "Thursday, August 31, 2006 1:14";
string[] formats = new string[] { "f" };
IFormatProvider provider = new CultureInfo("en-US");
DateTimeStyles style = DateTimeStyles.AssumeLocal | DateTimeStyles.AssumeUniversal;
AssertExtensions.Throws<ArgumentException>("style", () => DateTime.ParseExact(strDateTime, formats, provider, style));
}

Expand Down Expand Up @@ -2217,6 +2220,23 @@ public static IEnumerable<object[]> ParseExact_ValidInput_Succeeds_MemberData()
yield return new object[] { " 9 / 8 / 2017 10 : 11 : 12 AM", "M/d/yyyy HH':'mm':'ss tt\' \'", CultureInfo.InvariantCulture, DateTimeStyles.AllowWhiteSpaces, new DateTime(2017, 9, 8, 10, 11, 12) };
yield return new object[] { " 9 / 8 / 2017 10 : 11 : 12 AM", "M/d/yyyy HH':'mm':'ss tt\' \'", CultureInfo.InvariantCulture, DateTimeStyles.AllowWhiteSpaces, new DateTime(2017, 9, 8, 10, 11, 12) };

// RoundtripKind: preserves the UTC kind when parsing UTC strings (indicated by 'Z')
yield return new object[] { "2017-10-11T01:23:45Z", "yyyy-MM-dd'T'HH:mm:ssK", CultureInfo.InvariantCulture, DateTimeStyles.RoundtripKind, new DateTime(2017, 10, 11, 1, 23, 45, DateTimeKind.Utc) };
yield return new object[] { "2017-10-11T01:23:45.678Z", "yyyy-MM-dd'T'HH:mm:ss.fffK", CultureInfo.InvariantCulture, DateTimeStyles.RoundtripKind, new DateTime(2017, 10, 11, 1, 23, 45, 678, DateTimeKind.Utc) };
yield return new object[] { "2017-10-11T01:23:45.6789012Z", "O", CultureInfo.InvariantCulture, DateTimeStyles.RoundtripKind, null }; // roundtrip format

// AssumeLocal: interprets date/time as local when no timezone is specified
yield return new object[] { "2017-10-11 01:23:45", "yyyy-MM-dd HH:mm:ss", CultureInfo.InvariantCulture, DateTimeStyles.AssumeLocal, new DateTime(2017, 10, 11, 1, 23, 45, DateTimeKind.Local) };
yield return new object[] { "9/8/2017 10:11:12 AM", "M/d/yyyy h:mm:ss tt", CultureInfo.InvariantCulture, DateTimeStyles.AssumeLocal, new DateTime(2017, 9, 8, 10, 11, 12, DateTimeKind.Local) };

// NoCurrentDateDefault: uses 0001-01-01 instead of current date when date components are missing
yield return new object[] { "10:30:45", "HH:mm:ss", CultureInfo.InvariantCulture, DateTimeStyles.NoCurrentDateDefault, new DateTime(1, 1, 1, 10, 30, 45) };
yield return new object[] { "3:45 PM", "h:mm tt", CultureInfo.InvariantCulture, DateTimeStyles.NoCurrentDateDefault, new DateTime(1, 1, 1, 15, 45, 0) };

// AllowInnerWhite (standalone): allows white space to appear in the middle of the string
yield return new object[] { "2017 - 10 - 11 01:23:45", "yyyy-MM-dd HH:mm:ss", CultureInfo.InvariantCulture, DateTimeStyles.AllowInnerWhite, new DateTime(2017, 10, 11, 1, 23, 45) };
yield return new object[] { "9 / 8 / 2017 10 : 11 : 12", "M/d/yyyy HH:mm:ss", CultureInfo.InvariantCulture, DateTimeStyles.AllowInnerWhite, new DateTime(2017, 9, 8, 10, 11, 12) };

if (PlatformDetection.IsNotInvariantGlobalization)
{
var hebrewCulture = new CultureInfo("he-IL");
Expand Down
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