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.Net: [.NET] Add TimeProvider injection to TimePlugin for deterministic testing #14112

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6a874e1
Add TimeProvider injection to TimePlugin to enable deterministic unit…
grvnmttl Jun 23, 2026
427beb1
Address Copilot review feedback on TimePlugin PR
grvnmttl Jun 23, 2026
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43 changes: 27 additions & 16 deletions dotnet/src/Plugins/Plugins.Core/TimePlugin.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -14,6 +14,17 @@ namespace Microsoft.SemanticKernel.Plugins.Core;
/// </remark>
public sealed class TimePlugin
{
private readonly TimeProvider _timeProvider;

/// <summary>
/// Initializes a new instance of the <see cref="TimePlugin"/> class.
/// </summary>
/// <param name="timeProvider">The time provider to use. Defaults to <see cref="TimeProvider.System"/>.</param>
public TimePlugin(TimeProvider? timeProvider = null)
{
this._timeProvider = timeProvider ?? TimeProvider.System;
}
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/// <summary>
/// Get the current date
/// </summary>
Expand All @@ -24,7 +35,7 @@ public sealed class TimePlugin
[KernelFunction, Description("Get the current date")]
public string Date(IFormatProvider? formatProvider = null) =>
// Example: Sunday, 12 January, 2025
DateTimeOffset.Now.ToString("D", formatProvider);
this._timeProvider.GetLocalNow().ToString("D", formatProvider);

/// <summary>
/// Get the current date
Expand All @@ -48,7 +59,7 @@ public string Today(IFormatProvider? formatProvider = null) =>
[KernelFunction, Description("Get the current date and time in the local time zone")]
public string Now(IFormatProvider? formatProvider = null) =>
// Sunday, January 12, 2025 9:15 PM
DateTimeOffset.Now.ToString("f", formatProvider);
this._timeProvider.GetLocalNow().ToString("f", formatProvider);

/// <summary>
/// Get the current UTC date and time
Expand All @@ -60,7 +71,7 @@ public string Now(IFormatProvider? formatProvider = null) =>
[KernelFunction, Description("Get the current UTC date and time")]
public string UtcNow(IFormatProvider? formatProvider = null) =>
// Sunday, January 13, 2025 5:15 AM
DateTimeOffset.UtcNow.ToString("f", formatProvider);
this._timeProvider.GetUtcNow().ToString("f", formatProvider);

/// <summary>
/// Get the current time
Expand All @@ -72,7 +83,7 @@ public string UtcNow(IFormatProvider? formatProvider = null) =>
[KernelFunction, Description("Get the current time")]
public string Time(IFormatProvider? formatProvider = null) =>
// Example: 09:15:07 PM
DateTimeOffset.Now.ToString("hh:mm:ss tt", formatProvider);
this._timeProvider.GetLocalNow().ToString("hh:mm:ss tt", formatProvider);

/// <summary>
/// Get the current year
Expand All @@ -84,7 +95,7 @@ public string Time(IFormatProvider? formatProvider = null) =>
[KernelFunction, Description("Get the current year")]
public string Year(IFormatProvider? formatProvider = null) =>
// Example: 2025
DateTimeOffset.Now.ToString("yyyy", formatProvider);
this._timeProvider.GetLocalNow().ToString("yyyy", formatProvider);

/// <summary>
/// Get the current month name
Expand All @@ -96,7 +107,7 @@ public string Year(IFormatProvider? formatProvider = null) =>
[KernelFunction, Description("Get the current month name")]
public string Month(IFormatProvider? formatProvider = null) =>
// Example: January
DateTimeOffset.Now.ToString("MMMM", formatProvider);
this._timeProvider.GetLocalNow().ToString("MMMM", formatProvider);

/// <summary>
/// Get the current month number
Expand All @@ -108,7 +119,7 @@ public string Month(IFormatProvider? formatProvider = null) =>
[KernelFunction, Description("Get the current month number")]
public string MonthNumber(IFormatProvider? formatProvider = null) =>
// Example: 01
DateTimeOffset.Now.ToString("MM", formatProvider);
this._timeProvider.GetLocalNow().ToString("MM", formatProvider);

/// <summary>
/// Get the current day of the month
Expand All @@ -120,7 +131,7 @@ public string MonthNumber(IFormatProvider? formatProvider = null) =>
[KernelFunction, Description("Get the current day of the month")]
public string Day(IFormatProvider? formatProvider = null) =>
// Example: 12
DateTimeOffset.Now.ToString("dd", formatProvider);
this._timeProvider.GetLocalNow().ToString("dd", formatProvider);

/// <summary>
/// Get the date a provided number of days in the past
Expand All @@ -129,7 +140,7 @@ public string Day(IFormatProvider? formatProvider = null) =>
[KernelFunction]
[Description("Get the date offset by a provided number of days from today")]
public string DaysAgo([Description("The number of days to offset from today")] double input, IFormatProvider? formatProvider = null) =>
DateTimeOffset.Now.AddDays(-input).ToString("D", formatProvider);
this._timeProvider.GetLocalNow().AddDays(-input).ToString("D", formatProvider);

/// <summary>
/// Get the current day of the week
Expand All @@ -141,7 +152,7 @@ public string DaysAgo([Description("The number of days to offset from today")] d
[KernelFunction, Description("Get the current day of the week")]
public string DayOfWeek(IFormatProvider? formatProvider = null) =>
// Example: Sunday
DateTimeOffset.Now.ToString("dddd", formatProvider);
this._timeProvider.GetLocalNow().ToString("dddd", formatProvider);

/// <summary>
/// Get the current clock hour
Expand All @@ -153,7 +164,7 @@ public string DayOfWeek(IFormatProvider? formatProvider = null) =>
[KernelFunction, Description("Get the current clock hour")]
public string Hour(IFormatProvider? formatProvider = null) =>
// Example: 9 PM
DateTimeOffset.Now.ToString("h tt", formatProvider);
this._timeProvider.GetLocalNow().ToString("h tt", formatProvider);

/// <summary>
/// Get the current clock 24-hour number
Expand All @@ -165,7 +176,7 @@ public string Hour(IFormatProvider? formatProvider = null) =>
[KernelFunction, Description("Get the current clock 24-hour number")]
public string HourNumber(IFormatProvider? formatProvider = null) =>
// Example: 21
DateTimeOffset.Now.ToString("HH", formatProvider);
this._timeProvider.GetLocalNow().ToString("HH", formatProvider);

/// <summary>
/// Get the date of the previous day matching the supplied day name
Expand All @@ -181,7 +192,7 @@ public string DateMatchingLastDayName(
[Description("The day name to match")] DayOfWeek input,
IFormatProvider? formatProvider = null)
{
DateTimeOffset dateTime = DateTimeOffset.Now;
DateTimeOffset dateTime = this._timeProvider.GetLocalNow();

// Walk backwards from the previous day for up to a week to find the matching day
for (int i = 1; i <= 7; ++i)
Expand All @@ -206,7 +217,7 @@ public string DateMatchingLastDayName(
[KernelFunction, Description("Get the minutes on the current hour")]
public string Minute(IFormatProvider? formatProvider = null) =>
// Example: 15
DateTimeOffset.Now.ToString("mm", formatProvider);
this._timeProvider.GetLocalNow().ToString("mm", formatProvider);

/// <summary>
/// Get the seconds on the current minute
Expand All @@ -218,7 +229,7 @@ public string Minute(IFormatProvider? formatProvider = null) =>
[KernelFunction, Description("Get the seconds on the current minute")]
public string Second(IFormatProvider? formatProvider = null) =>
// Example: 07
DateTimeOffset.Now.ToString("ss", formatProvider);
this._timeProvider.GetLocalNow().ToString("ss", formatProvider);

/// <summary>
/// Get the local time zone offset from UTC
Expand All @@ -230,7 +241,7 @@ public string Second(IFormatProvider? formatProvider = null) =>
[KernelFunction, Description("Get the local time zone offset from UTC")]
public string TimeZoneOffset(IFormatProvider? formatProvider = null) =>
// Example: -08:00
DateTimeOffset.Now.ToString("%K", formatProvider);
this._timeProvider.GetLocalNow().ToString("%K", formatProvider);

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/// <summary>
/// Get the local time zone name
Expand Down
170 changes: 123 additions & 47 deletions dotnet/src/Plugins/Plugins.UnitTests/Core/TimePluginTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -11,44 +11,150 @@

namespace SemanticKernel.Plugins.UnitTests.Core;

// TODO: allow clock injection and test all functions
public class TimePluginTests
{
// Sunday, 15 June 2025 21:15:07 UTC — local timezone pinned to UTC so tests are machine-independent
private static readonly DateTimeOffset s_fixedTime = new(2025, 6, 15, 21, 15, 7, TimeSpan.Zero);

private static TimePlugin CreatePlugin() => new(new FixedUtcTimeProvider(s_fixedTime));

/// <summary>Minimal TimeProvider that returns a fixed UTC instant with UTC as local timezone.</summary>
private sealed class FixedUtcTimeProvider(DateTimeOffset fixedUtc) : TimeProvider
{
public override DateTimeOffset GetUtcNow() => fixedUtc.ToUniversalTime();
public override TimeZoneInfo LocalTimeZone => TimeZoneInfo.Utc;
}

[Fact]
public void ItCanBeInstantiated()
{
// Act - Assert no exception occurs
var _ = new TimePlugin();
}

[Fact]
public void ItCanBeImported()
{
// Act - Assert no exception occurs e.g. due to reflection
Assert.NotNull(KernelPluginFactory.CreateFromType<TimePlugin>("time"));
}

[Fact]
public void DaysAgo()
public void Date()
{
// InvariantCulture "D" format: dddd, dd MMMM yyyy
Assert.Equal("Sunday, 15 June 2025", CreatePlugin().Date(CultureInfo.InvariantCulture));
}

[Fact]
public void Today()
{
double interval = 2;
DateTime expected = DateTime.Now.AddDays(-interval);
var plugin = new TimePlugin();
string result = plugin.DaysAgo(interval, CultureInfo.CurrentCulture);
DateTime returned = DateTime.Parse(result, CultureInfo.CurrentCulture);
Assert.Equal(expected.Day, returned.Day);
Assert.Equal(expected.Month, returned.Month);
Assert.Equal(expected.Year, returned.Year);
Assert.Equal("Sunday, 15 June 2025", CreatePlugin().Today(CultureInfo.InvariantCulture));
}

[Fact]
public void Now()
{
// InvariantCulture "f" format: dddd, dd MMMM yyyy HH:mm
Assert.Equal("Sunday, 15 June 2025 21:15", CreatePlugin().Now(CultureInfo.InvariantCulture));
}

[Fact]
public void UtcNow()
{
Assert.Equal("Sunday, 15 June 2025 21:15", CreatePlugin().UtcNow(CultureInfo.InvariantCulture));
}

[Fact]
public void Time()
{
Assert.Equal("09:15:07 PM", CreatePlugin().Time(CultureInfo.InvariantCulture));
}

[Fact]
public void Year()
{
Assert.Equal("2025", CreatePlugin().Year(CultureInfo.InvariantCulture));
}

[Fact]
public void Month()
{
Assert.Equal("June", CreatePlugin().Month(CultureInfo.InvariantCulture));
}

[Fact]
public void MonthNumber()
{
Assert.Equal("06", CreatePlugin().MonthNumber(CultureInfo.InvariantCulture));
}

[Fact]
public void Day()
{
string expected = DateTime.Now.ToString("dd", CultureInfo.CurrentCulture);
var plugin = new TimePlugin();
string result = plugin.Day(CultureInfo.CurrentCulture);
Assert.Equal(expected, result);
Assert.True(int.TryParse(result, out _));
Assert.Equal("15", CreatePlugin().Day(CultureInfo.InvariantCulture));
}

[Fact]
public void DayOfWeek()
{
Assert.Equal("Sunday", CreatePlugin().DayOfWeek(CultureInfo.InvariantCulture));
}

[Fact]
public void Hour()
{
Assert.Equal("9 PM", CreatePlugin().Hour(CultureInfo.InvariantCulture));
}

[Fact]
public void HourNumber()
{
Assert.Equal("21", CreatePlugin().HourNumber(CultureInfo.InvariantCulture));
}

[Fact]
public void Minute()
{
Assert.Equal("15", CreatePlugin().Minute(CultureInfo.InvariantCulture));
}

[Fact]
public void Second()
{
Assert.Equal("07", CreatePlugin().Second(CultureInfo.InvariantCulture));
}

[Fact]
public void TimeZoneOffset()
{
Assert.Equal("+00:00", CreatePlugin().TimeZoneOffset(CultureInfo.InvariantCulture));
}

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[Fact]
public void DaysAgo()
{
// 2 days before 2025-06-15 is 2025-06-13 (Friday)
Assert.Equal("Friday, 13 June 2025", CreatePlugin().DaysAgo(2, CultureInfo.InvariantCulture));
}

[Theory]
[MemberData(nameof(DayOfWeekCases))]
public void DateMatchingLastDayName(DayOfWeek dayName, string expectedDate)
{
// Fixed time is Sunday 2025-06-15; walk back to find each day
Assert.Equal(expectedDate, CreatePlugin().DateMatchingLastDayName(dayName, CultureInfo.InvariantCulture));
}

public static IEnumerable<object[]> DayOfWeekCases()
{
// From Sunday 2025-06-15, the previous occurrence of each day (never same day).
// InvariantCulture "D" format: dddd, dd MMMM yyyy
yield return [System.DayOfWeek.Saturday, "Saturday, 14 June 2025"];
yield return [System.DayOfWeek.Friday, "Friday, 13 June 2025"];
yield return [System.DayOfWeek.Thursday, "Thursday, 12 June 2025"];
yield return [System.DayOfWeek.Wednesday, "Wednesday, 11 June 2025"];
yield return [System.DayOfWeek.Tuesday, "Tuesday, 10 June 2025"];
yield return [System.DayOfWeek.Monday, "Monday, 09 June 2025"];
yield return [System.DayOfWeek.Sunday, "Sunday, 08 June 2025"];
}

[Fact]
Expand All @@ -60,34 +166,4 @@ public async Task LastMatchingDayBadInputAsync()

AssertExtensions.AssertIsArgumentOutOfRange(ex, "input", "not a day name");
}

[Theory]
[MemberData(nameof(DayOfWeekEnumerator))]
public void LastMatchingDay(DayOfWeek dayName)
{
int steps = 0;
DateTime date = DateTime.Now.Date.AddDays(-1);
while (date.DayOfWeek != dayName && steps <= 7)
{
date = date.AddDays(-1);
steps++;
}
bool found = date.DayOfWeek == dayName;
Assert.True(found);

var plugin = new TimePlugin();
string result = plugin.DateMatchingLastDayName(dayName, CultureInfo.CurrentCulture);
DateTime returned = DateTime.Parse(result, CultureInfo.CurrentCulture);
Assert.Equal(date.Day, returned.Day);
Assert.Equal(date.Month, returned.Month);
Assert.Equal(date.Year, returned.Year);
}

public static IEnumerable<object[]> DayOfWeekEnumerator()
{
foreach (var day in Enum.GetValues<DayOfWeek>())
{
yield return new object[] { day };
}
}
}
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