Add Screen/SystemInformation tests (#1530)

* Add Screen/SystemInformation tests

* Fix a NRE in Screen.FromControl

src/System.Windows.Forms/src/System/Windows/Forms/Screen.cs

@@ -331,7 +331,15 @@ public static Screen FromRectangle(Rectangle rect)
         ///  Retrieves a <see cref='Screen'/> for the monitor that contains
         ///  the largest region of the window of the control.
         /// </summary>
-        public static Screen FromControl(Control control) => FromHandle(control.Handle);
+        public static Screen FromControl(Control control)
+        {
+            if (control == null)
+            {
+                throw new ArgumentNullException(nameof(control));
+            }
+
+            return FromHandle(control.Handle);
+        }
 
         /// <summary>
         ///  Retrieves a <see cref='Screen'/> for the monitor that contains

src/System.Windows.Forms/tests/UnitTests/System/Windows/Forms/ScreenTests.cs

@@ -0,0 +1,221 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Generic;
+using System.Drawing;
+using Xunit;
+
+namespace System.Windows.Forms.Tests
+{
+    public class ScreenTests
+    {
+        [Fact]
+        public void Screen_AllScreens_Get_ReturnsExpected()
+        {
+            Screen[] screens = Screen.AllScreens;
+            Assert.NotEmpty(screens);
+            Assert.Same(screens, Screen.AllScreens);
+
+            foreach (Screen screen in screens)
+            {
+                VerifyScreen(screen);
+            }
+
+            Assert.Contains(screens, s => s.Primary);
+        }
+
+        [Fact]
+        public void Screen_PrimaryScreen_Get_ReturnsExpected()
+        {
+            Screen screen = Screen.PrimaryScreen;
+            Assert.NotNull(screen);
+            VerifyScreen(screen);
+        }
+
+        public static IEnumerable<object[]> Equals_Screen_TestData()
+        {
+            var screen = new Screen((IntPtr)1);
+            yield return new object[] { screen, screen, true };
+            yield return new object[] { screen, new Screen((IntPtr)1), true };
+            yield return new object[] { screen, new Screen((IntPtr)2), false };
+        }
+
+        public static IEnumerable<object[]> Equals_Object_TestData()
+        {
+            var screen = new Screen((IntPtr)1);
+            yield return new object[] { screen, new object(), false };
+            yield return new object[] { screen, null, false };
+        }
+
+        [Theory]
+        [MemberData(nameof(Equals_Screen_TestData))]
+        [MemberData(nameof(Equals_Object_TestData))]
+        public void Screen_Equals_Invoke_ReturnsExpected(Screen screen, object obj, bool expected)
+        {
+            Assert.Equal(expected, screen.Equals(obj));
+        }
+
+        [Theory]
+        [MemberData(nameof(Equals_Screen_TestData))]
+        public void Screen_GetHashCode_Invoke_ReturnsExpected(Screen screen1, Screen screen2, bool expected)
+        {
+            Assert.Equal(expected, screen1.GetHashCode().Equals(screen2.GetHashCode()));
+        }
+
+        public static IEnumerable<object[]> FromControl_TestData()
+        {
+            yield return new object[] { new Control() };
+
+            var createdControl = new Control();
+            Assert.NotEqual(IntPtr.Zero, createdControl.Handle);
+            yield return new object[] { createdControl };
+        }
+
+        [Theory]
+        [MemberData(nameof(FromControl_TestData))]
+        public void Screen_FromControl_Invoke_ReturnsExpected(Control control)
+        {
+            Screen screen = Screen.FromControl(control);
+            Assert.NotNull(screen);
+            VerifyScreen(screen);
+        }
+
+        [Fact]
+        public void Screen_FromControl_NullControl_ThrowsArgumentNullException()
+        {
+            Assert.Throws<ArgumentNullException>("control", () => Screen.FromControl(null));
+        }
+
+        public static IEnumerable<object[]> FromHandle_TestData()
+        {
+            yield return new object[] { IntPtr.Zero };
+            yield return new object[] { new Control().Handle };
+        }
+
+        [Theory]
+        [MemberData(nameof(FromHandle_TestData))]
+        public void Screen_FromHandle_Invoke_ReturnsExpected(IntPtr handle)
+        {
+            Screen screen = Screen.FromHandle(handle);
+            Assert.NotNull(screen);
+            VerifyScreen(screen);
+        }
+
+        public static IEnumerable<object[]> FromPoint_TestData()
+        {
+            yield return new object[] { new Point(-1, -2) };
+            yield return new object[] { new Point(0, 0) };
+            yield return new object[] { new Point(1, 2) };
+            yield return new object[] { new Point(int.MaxValue, int.MaxValue) };
+        }
+
+        [Theory]
+        [MemberData(nameof(FromPoint_TestData))]
+        public void Screen_FromPoint_Invoke_ReturnsExpected(Point point)
+        {
+            Screen screen = Screen.FromPoint(point);
+            Assert.NotNull(screen);
+            VerifyScreen(screen);
+        }
+
+        public static IEnumerable<object[]> FromRectangle_TestData()
+        {
+            yield return new object[] { new Rectangle(-1, -2, -3, -4) };
+            yield return new object[] { new Rectangle(0, 0, 0, 0) };
+            yield return new object[] { new Rectangle(1, 2, 3, 4) };
+            yield return new object[] { new Rectangle(int.MaxValue, int.MaxValue, int.MaxValue, int.MaxValue) };
+        }
+
+        [Theory]
+        [MemberData(nameof(FromRectangle_TestData))]
+        public void Screen_FromRectangle_Invoke_ReturnsExpected(Rectangle rectangle)
+        {
+            Screen screen = Screen.FromRectangle(rectangle);
+            Assert.NotNull(screen);
+            VerifyScreen(screen);
+        }
+
+        [Theory]
+        [MemberData(nameof(FromControl_TestData))]
+        public void Screen_GetBounds_InvokeControl_ReturnsExpected(Control control)
+        {
+            Screen screen = Screen.FromControl(control);
+            Assert.Equal(screen.Bounds, Screen.GetBounds(control));
+        }
+
+        [Theory]
+        [MemberData(nameof(FromPoint_TestData))]
+        public void Screen_GetBounds_InvokePoint_ReturnsExpected(Point point)
+        {
+            Screen screen = Screen.FromPoint(point);
+            Assert.Equal(screen.Bounds, Screen.GetBounds(point));
+        }
+
+        [Theory]
+        [MemberData(nameof(FromRectangle_TestData))]
+        public void Screen_GetBounds_InvokeRectangle_ReturnsExpected(Rectangle rectangle)
+        {
+            Screen screen = Screen.FromRectangle(rectangle);
+            Assert.Equal(screen.Bounds, Screen.GetBounds(rectangle));
+        }
+
+        [Fact]
+        public void Screen_GetBounds_NullControl_ThrowsArgumentNullException()
+        {
+            Assert.Throws<ArgumentNullException>("control", () => Screen.GetBounds(null));
+        }
+
+        [Theory]
+        [MemberData(nameof(FromControl_TestData))]
+        public void Screen_GetWorkingArea_InvokeControl_ReturnsExpected(Control control)
+        {
+            Screen screen = Screen.FromControl(control);
+            Assert.Equal(screen.WorkingArea, Screen.GetWorkingArea(control));
+        }
+
+        [Theory]
+        [MemberData(nameof(FromPoint_TestData))]
+        public void Screen_GetWorkingArea_InvokePoint_ReturnsExpected(Point point)
+        {
+            Screen screen = Screen.FromPoint(point);
+            Assert.Equal(screen.WorkingArea, Screen.GetWorkingArea(point));
+        }
+
+        [Theory]
+        [MemberData(nameof(FromRectangle_TestData))]
+        public void Screen_GetWorkingArea_InvokeRectangle_ReturnsExpected(Rectangle rectangle)
+        {
+            Screen screen = Screen.FromRectangle(rectangle);
+            Assert.Equal(screen.WorkingArea, Screen.GetWorkingArea(rectangle));
+        }
+
+        [Fact]
+        public void Screen_GetWorkingArea_NullControl_ThrowsArgumentNullException()
+        {
+            Assert.Throws<ArgumentNullException>("control", () => Screen.GetWorkingArea(null));
+        }
+
+        [Fact]
+        public void Screen_ToString_Invoke_ReturnsExpected()
+        {
+            Screen screen = Screen.PrimaryScreen;
+            Assert.Equal($"Screen[Bounds={screen.Bounds} WorkingArea={screen.WorkingArea} Primary=True DeviceName={screen.DeviceName}", screen.ToString());
+        }
+
+        private static void VerifyScreen(Screen screen)
+        {
+            Assert.Contains(screen.BitsPerPixel, new int[] { 1, 2, 4, 8, 16, 24, 32, 48, 64 });
+            Assert.True(screen.Bounds.X >= 0);
+            Assert.True(screen.Bounds.Y >= 0);
+            Assert.True(screen.Bounds.Width > 0);
+            Assert.True(screen.Bounds.Height > 0);
+            Assert.InRange(screen.DeviceName.Length, 1, 32);
+            Assert.Equal(screen.DeviceName, screen.DeviceName.Trim('\0'));
+            Assert.True(screen.WorkingArea.X >= 0);
+            Assert.True(screen.WorkingArea.Y >= 0);
+            Assert.InRange(screen.WorkingArea.Width, 1, screen.Bounds.Width);
+            Assert.InRange(screen.WorkingArea.Height, 1, screen.Bounds.Height);
+        }
+    }
+}