Write CalendarExtensionsTests.

FoundationExtras/Tests/FoundationExtrasTests/CalendarExtensionsTests.swift

@@ -0,0 +1,39 @@
+//
+//  CalendarExtensionsTests.swift
+//  
+//
+//  Created by Brent Simmons on 5/18/24.
+//
+
+import XCTest
+
+final class CalendarExtensionsTests: XCTestCase {
+
+	// MARK: - Test dateIsToday
+
+	func testDateIsToday() {
+
+		var date = Date()
+		// The below could fail if midnight hits between the above line and the following line! This will probably never happen, but if it does, check to see if this was run at midnight.
+		XCTAssertTrue(Calendar.dateIsToday(date))
+
+		date = Date.distantPast
+		XCTAssertFalse(Calendar.dateIsToday(date))
+
+		date = Date.distantFuture
+		XCTAssertFalse(Calendar.dateIsToday(date))
+
+		date = Date().byAdding(days: 14)
+		XCTAssertFalse(Calendar.dateIsToday(date))
+
+		date = Date().bySubtracting(days: 67)
+		XCTAssertFalse(Calendar.dateIsToday(date))
+
+		let calendar = Calendar.current
+		let yesterday = calendar.date(byAdding: .day, value: -1, to: Date())!
+		XCTAssertFalse(Calendar.dateIsToday(yesterday))
+
+		let tomorrow = calendar.date(byAdding: .day, value: 1, to: Date())!
+		XCTAssertFalse(Calendar.dateIsToday(tomorrow))
+	}
+ }