Add tests for formatter

Sources/ExtendedDatePickerFormatter.swift

@@ -1,6 +1,6 @@
 import Foundation
 
-public class ExtendedDatePickerFormatter {
+final class ExtendedDatePickerFormatter {
   private let dateFormatter: DateFormatter
   private let dateIntervalFormatter: DateIntervalFormatter
   private let calendar: Calendar

Tests/ExtendedDatePickerFormatterTests.swift

@@ -0,0 +1,165 @@
+@testable import ExtendedDatePicker
+import XCTest
+
+final class ExtendedDatePickerFormatterTests: XCTestCase {
+
+  private var sut: ExtendedDatePickerFormatter!
+  private var calendar: Calendar = .current
+
+  func testHourMode_shouldOnlyDisplayHour() {
+    // Arrange
+    self.calendar.locale = .init(identifier: "en-GB")
+    self.sut = .init(calendar: calendar)
+
+    let hour = calendar.date(
+      from: .init(
+        year: 2024,
+        month: 7,
+        day: 15,
+        hour: 17
+      )
+    )!
+
+    // Act
+    let result = sut.format(from: hour, mode: .hour)
+
+    // Assert
+    XCTAssertEqual(result, "17:00")
+  }
+
+  func testDateMode_shouldOnlyDisplayDate() {
+      // Arrange
+    self.calendar.locale = .init(identifier: "en-US")
+    self.sut = .init(calendar: calendar)
+
+    let hour = calendar.date(
+      from: .init(
+        year: 2024,
+        month: 7,
+        day: 15,
+        hour: 17,
+        minute: 37
+      )
+    )!
+
+      // Act
+    let result = sut.format(from: hour, mode: .date)
+
+      // Assert
+    XCTAssertEqual(result, "July 15, 2024")
+  }
+
+  func testDateTimeMode_shouldDisplayBothDateAndTime() {
+      // Arrange
+    self.calendar.locale = .init(identifier: "en-US")
+    self.sut = .init(calendar: calendar)
+
+    let hour = calendar.date(
+      from: .init(
+        year: 2024,
+        month: 7,
+        day: 15,
+        hour: 17,
+        minute: 37
+      )
+    )!
+
+      // Act
+    let result = sut.format(from: hour, mode: .dateTime)
+
+      // Assert
+    XCTAssertEqual(result, "July 15, 2024 at 5:37 PM")
+  }
+
+  func testDateTimeMode_givenENGBLocale_shouldDisplayBothDateAndTime() {
+      // Arrange
+    self.calendar.locale = .init(identifier: "en-GB")
+    self.sut = .init(calendar: calendar)
+
+    let hour = calendar.date(
+      from: .init(
+        year: 2024,
+        month: 7,
+        day: 15,
+        hour: 17,
+        minute: 37
+      )
+    )!
+
+      // Act
+    let result = sut.format(from: hour, mode: .dateTime)
+
+      // Assert
+    XCTAssertEqual(result, "15 July 2024 at 17:37")
+  }
+
+  func testWeekMode_shouldDisplayDayRange() {
+      // Arrange
+    self.calendar.locale = .init(identifier: "en-GB")
+    self.sut = .init(calendar: calendar)
+
+    let hour = calendar.date(
+      from: .init(
+        year: 2024,
+        month: 7,
+        day: 15,
+        hour: 17,
+        minute: 37
+      )
+    )!
+
+      // Act
+    let result = sut.format(from: hour, mode: .week)
+
+      // Assert
+    XCTAssertEqual(result, "15 – 21 Jul 2024")
+  }
+
+
+
+  func testMonthYearMode_shouldNotDisplayDay() {
+      // Arrange
+    self.calendar.locale = .init(identifier: "en-US")
+    self.sut = .init(calendar: calendar)
+
+    let hour = calendar.date(
+      from: .init(
+        year: 2024,
+        month: 7,
+        day: 15,
+        hour: 17,
+        minute: 37
+      )
+    )!
+
+      // Act
+    let result = sut.format(from: hour, mode: .monthYear)
+
+      // Assert
+    XCTAssertEqual(result, "July 2024")
+  }
+
+  func testYearMode_shouldNotDisplayMonth() {
+      // Arrange
+    self.calendar.locale = .init(identifier: "en-US")
+    self.sut = .init(calendar: calendar)
+
+    let hour = calendar.date(
+      from: .init(
+        year: 2024,
+        month: 7,
+        day: 15,
+        hour: 17,
+        minute: 37
+      )
+    )!
+
+      // Act
+    let result = sut.format(from: hour, mode: .year)
+
+      // Assert
+    XCTAssertEqual(result, "2024")
+  }
+
+
+}