Final Test - [Null Elements]

NullElements/NullElements.Tests/BasicListTests.cs

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+// <copyright file="BasicListTests.cs" company="Ilya Krivtsov">
+// Copyright (c) Ilya Krivtsov. All rights reserved.
+// </copyright>
+
+namespace NullElements.Tests;
+
+public class BasicListTests
+{
+    private BasicList<int> list;
+
+    [SetUp]
+    public void Setup()
+    {
+        list = [];
+    }
+
+    [Test]
+    public void EmptyList_ShouldReturn_EmptyEnumerator()
+    {
+        Assert.That(list.SequenceEqual([]), Is.True);
+    }
+
+    [Test]
+    public void ListWithOneValue_ShouldReturn_EnumeratorWithOneElement()
+    {
+        int value = 42;
+        list.Add(value);
+        Assert.That(list.SequenceEqual([value]), Is.True);
+    }
+
+    [Test]
+    public void ListWithManyValues_ShouldReturn_EnumeratorWithSameValules()
+    {
+        var values = Enumerable.Range(0, 1000);
+        foreach (var value in values)
+        {
+            list.Add(value);
+        }
+
+        Assert.That(list.SequenceEqual(values), Is.True);
+    }
+
+    [Test]
+    public void ModifyingList_WhileIterating_ShouldThrow()
+    {
+        var values = Enumerable.Range(0, 1000);
+        foreach (var value in values)
+        {
+            list.Add(value);
+        }
+
+        var enumerator = list.GetEnumerator();
+        enumerator.MoveNext();
+        list.Add(1010101);
+        Assert.Throws<InvalidOperationException>(() => enumerator.MoveNext());
+    }
+}

NullElements/NullElements.Tests/GlobalSuppressions.cs

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+// <copyright file="GlobalSuppressions.cs" company="Ilya Krivtsov">
+// Copyright (c) Ilya Krivtsov. All rights reserved.
+// </copyright>
+
+// This file is used by Code Analysis to maintain SuppressMessage
+// attributes that are applied to this project.
+// Project-level suppressions either have no target or are given
+// a specific target and scoped to a namespace, type, member, etc.
+using System.Diagnostics.CodeAnalysis;
+
+[assembly: SuppressMessage("StyleCop.CSharp.DocumentationRules", "SA1600:Elements should be documented", Justification = "This is project with tests")]

NullElements/NullElements.Tests/NullElements.Tests.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net9.0</TargetFramework>
+    <LangVersion>latest</LangVersion>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+    <IsPackable>false</IsPackable>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="coverlet.collector" Version="6.0.2" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.12.0" />
+    <PackageReference Include="NUnit" Version="4.2.2" />
+    <PackageReference Include="NUnit.Analyzers" Version="4.4.0" />
+    <PackageReference Include="NUnit3TestAdapter" Version="4.6.0" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <Using Include="NUnit.Framework" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="../NullElements/NullElements.csproj" />
+  </ItemGroup>
+
+</Project>

NullElements/NullElements.Tests/NullElementsTests.cs

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+// <copyright file="NullElementsTests.cs" company="Ilya Krivtsov">
+// Copyright (c) Ilya Krivtsov. All rights reserved.
+// </copyright>
+
+namespace NullElements.Tests;
+
+using System.Numerics;
+
+public class NullElementsTests
+{
+    [Test]
+    public void CountNullElements_IsCorrect_ForReferenceTypes()
+    {
+        BasicList<object> list = [null, 42, null, "abc", null];
+        Assert.That(list.CountNullElements(new ReferenceNullComparer<object>()), Is.EqualTo(3));
+    }
+
+    [Test]
+    public void CountNullElements_IsCorrect_ForNumberTypes()
+    {
+        BasicList<int> intList = [0, 1, 0, 2, 0, 100, 0, -100];
+        Assert.That(intList.CountNullElements(new NumberNullComparer<int>()), Is.EqualTo(4));
+
+        BasicList<float> floatList = [0, 0.1f, 0, 0.2f, 0, 100.100f, 0, -42.42f, 0.00000001f, 0];
+        Assert.That(floatList.CountNullElements(new NumberNullComparer<float>()), Is.EqualTo(5));
+    }
+
+    [Test]
+    public void CountNullElements_IsCorrect_ForStrings()
+    {
+        BasicList<string> list = [null, string.Empty, "abc", "def", null, "apple", string.Empty];
+        Assert.That(list.CountNullElements(new StringNullComparer()), Is.EqualTo(4));
+    }
+
+    private class ReferenceNullComparer<T> : INullComparer<T>
+        where T : class
+    {
+        public bool IsNull(T item) => item == null;
+    }
+
+    private class NumberNullComparer<T> : INullComparer<T>
+        where T : INumber<T>
+    {
+        public bool IsNull(T item) => T.IsZero(item);
+    }
+
+    private class StringNullComparer : INullComparer<string>
+    {
+        public bool IsNull(string item) => string.IsNullOrEmpty(item);
+    }
+}

NullElements/NullElements.sln

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+
+Microsoft Visual Studio Solution File, Format Version 12.00
+# Visual Studio Version 17
+VisualStudioVersion = 17.0.31903.59
+MinimumVisualStudioVersion = 10.0.40219.1
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "NullElements", "NullElements\NullElements.csproj", "{2F421D0B-CDA8-4ED3-BE33-4746FDB67D9D}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "NullElements.Tests", "NullElements.Tests\NullElements.Tests.csproj", "{D8B1FAB8-D74A-4D16-A79C-558BE5680BA7}"
+EndProject
+Global
+	GlobalSection(SolutionConfigurationPlatforms) = preSolution
+		Debug|Any CPU = Debug|Any CPU
+		Release|Any CPU = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(SolutionProperties) = preSolution
+		HideSolutionNode = FALSE
+	EndGlobalSection
+	GlobalSection(ProjectConfigurationPlatforms) = postSolution
+		{2F421D0B-CDA8-4ED3-BE33-4746FDB67D9D}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{2F421D0B-CDA8-4ED3-BE33-4746FDB67D9D}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{2F421D0B-CDA8-4ED3-BE33-4746FDB67D9D}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{2F421D0B-CDA8-4ED3-BE33-4746FDB67D9D}.Release|Any CPU.Build.0 = Release|Any CPU
+		{D8B1FAB8-D74A-4D16-A79C-558BE5680BA7}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{D8B1FAB8-D74A-4D16-A79C-558BE5680BA7}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{D8B1FAB8-D74A-4D16-A79C-558BE5680BA7}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{D8B1FAB8-D74A-4D16-A79C-558BE5680BA7}.Release|Any CPU.Build.0 = Release|Any CPU
+	EndGlobalSection
+EndGlobal

NullElements/NullElements/BasicList.cs

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+// <copyright file="BasicList.cs" company="Ilya Krivtsov">
+// Copyright (c) Ilya Krivtsov. All rights reserved.
+// </copyright>
+
+namespace NullElements;
+
+using System.Collections;
+
+/// <summary>
+/// Basic array-backed list.
+/// </summary>
+/// <typeparam name="T">Type of items.</typeparam>
+public class BasicList<T> : IEnumerable<T>
+{
+    private T[] values = new T[4];
+    private int count = 0;
+    private int version = 0;
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="BasicList{T}"/> class.
+    /// </summary>
+    public BasicList()
+    {
+        values = new T[4];
+        count = 0;
+    }
+
+    /// <summary>
+    /// Adds item to the list.
+    /// </summary>
+    /// <param name="item">Item to add.</param>
+    public void Add(T item)
+    {
+        if (count >= values.Length)
+        {
+            var newValues = new T[values.Length * 2];
+            Array.Copy(values, newValues, values.Length);
+            values = newValues;
+        }
+
+        values[count] = item;
+        count++;
+        version++;
+    }
+
+    /// <inheritdoc/>
+    public IEnumerator<T> GetEnumerator()
+    {
+        int lastVersion = version;
+
+        for (int i = 0; i < count; i++)
+        {
+            if (version != lastVersion)
+            {
+                throw new InvalidOperationException();
+            }
+
+            yield return values[i];
+        }
+    }
+
+    /// <inheritdoc/>
+    IEnumerator IEnumerable.GetEnumerator()
+    {
+        return GetEnumerator();
+    }
+}

NullElements/NullElements/INullComparer.cs

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+// <copyright file="INullComparer.cs" company="Ilya Krivtsov">
+// Copyright (c) Ilya Krivtsov. All rights reserved.
+// </copyright>
+
+namespace NullElements;
+
+/// <summary>
+/// Interface that can be used to check whether object is null.
+/// </summary>
+/// <typeparam name="T">Type of object to check.</typeparam>
+public interface INullComparer<T>
+{
+    /// <summary>
+    /// Checks whether specified object is null.
+    /// </summary>
+    /// <param name="item">Object to check.</param>
+    /// <returns><see langword="true"/> if specified object is null, <see langword="false"/> otherwise.</returns>
+    public bool IsNull(T item);
+}

NullElements/NullElements/NullElements.cs

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+// <copyright file="NullElements.cs" company="Ilya Krivtsov">
+// Copyright (c) Ilya Krivtsov. All rights reserved.
+// </copyright>
+
+namespace NullElements;
+
+/// <summary>
+/// Extension class that contains <c>CountNullElements</c> function.
+/// </summary>
+public static class NullElements
+{
+    /// <summary>
+    /// Counts null elements in the list.
+    /// </summary>
+    /// <typeparam name="T">Type of objects.</typeparam>
+    /// <param name="list">List to count objects from.</param>
+    /// <param name="comparer">Comparer that checks whether object is null.</param>
+    /// <returns>Count of null elements.</returns>
+    public static int CountNullElements<T>(this BasicList<T> list, INullComparer<T> comparer)
+        => list.Count(comparer.IsNull);
+}

NullElements/NullElements/NullElements.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net9.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+</Project>