Sybil/Sybil.UnitTests/FieldBuilderTests.cs

using FluentAssertions;
using Microsoft.CodeAnalysis.CSharp.Syntax;
using Microsoft.VisualStudio.TestTools.UnitTesting;
using System;

namespace Sybil.Tests;

[TestClass]
public class FieldBuilderTests
{
    private const string Public = "public";
    private const string PublicSealed = "public sealed";
    private const string FieldName = "someString";
    private const string FieldType = "string";
    private const string PublicField = "public string someString;";
    private const string PublicSealedField = "public sealed string someString;";

    private readonly FieldBuilder builder;

    public FieldBuilderTests()
    {
        this.builder = new FieldBuilder(FieldType, FieldName);
    }

    [TestMethod]
    public void Constructor_NullFieldType_ThrowsArgumentNullException()
    {
        var action = () =>
        {
            _ = new FieldBuilder(null, FieldName);
        };

        action.Should().Throw<ArgumentNullException>();
    }

    [TestMethod]
    public void Constructor_NullFieldName_ThrowsArgumentNullException()
    {
        var action = () =>
        {
            _ = new FieldBuilder(FieldType, null);
        };

        action.Should().Throw<ArgumentNullException>();
    }

    [TestMethod]
    public void WithModifier_ModifierNull_ThrowsArgumentNullException()
    {
        var action = () =>
        {
            this.builder.WithModifier(null);
        };

        action.Should().Throw<ArgumentNullException>();
    }

    [TestMethod]
    public void WithModifier_ModifierValid_ReturnsBuilder()
    {
        var returnedBuilder = this.builder.WithModifier(Public);

        returnedBuilder.Should().NotBeNull().And.Subject.Should().Be(this.builder);
    }

    [TestMethod]
    public void WithModifiers_ModifiersNull_ThrowsArgumentNullException()
    {
        var action = () =>
        {
            this.builder.WithModifiers(null);
        };

        action.Should().Throw<ArgumentNullException>();
    }

    [TestMethod]
    public void WithModifiers_ModifiersValid_ReturnsBuilder()
    {
        var returnedBuilder = this.builder.WithModifiers(PublicSealed);

        returnedBuilder.Should().NotBeNull().And.Subject.Should().Be(this.builder);
    }

    [TestMethod]
    public void Build_ReturnsFieldDeclarationSyntax()
    {
        var syntax = this.builder.Build();

        syntax.Should().NotBeNull().And.Subject.Should().BeOfType<FieldDeclarationSyntax>();
    }

    [TestMethod]
    public void WithModifier_ReturnsExpectedString()
    {
        var result = this.builder.WithModifier(Public).Build().ToFullString();

        result.Should().Be(PublicField);
    }

    [TestMethod]
    public void WithModifiers_ReturnsExpectedString()
    {
        var result = this.builder.WithModifiers(PublicSealed).Build().ToFullString();

        result.Should().Be(PublicSealedField);
    }
}