UA-.NETStandard/tests/Opc.Ua.SourceGeneration.Core.Tests/Generators/TextFileResourceTests.cs

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using System;
using System.IO;
using Moq;
using NUnit.Framework;

namespace Opc.Ua.SourceGeneration.Generator.Tests
{
    /// <summary>
    /// Unit tests for the TextFileResource class.
    /// </summary>
    [TestFixture]
    [Category("Generator")]
    [SetCulture("en-us")]
    [SetUICulture("en-us")]
    [Parallelizable]
    public class TextFileResourceTests
    {
        /// <summary>
        /// Tests that GetLength returns the expected file length from the file system.
        /// </summary>
        /// <param name = "fileName">The file name to test with.</param>
        /// <param name = "expectedLength">The expected length value that the file system should return.</param>
        [TestCase("test.txt", 100L)]
        [TestCase("file.xml", 0L)]
        [TestCase("large.bin", long.MaxValue)]
        [TestCase("C:\\path\\to\\file.txt", 12345L)]
        [TestCase("../relative/path.txt", 999L)]
        [TestCase("file-with-special-chars_@#$.txt", 42L)]
        public void GetLength_ValidFileSystemAndFileName_ReturnsExpectedLength(string fileName, long expectedLength)
        {
            // Arrange
            var mockFileSystem = new Mock<IFileSystem>();
            mockFileSystem.Setup(fs => fs.GetLength(fileName)).Returns(expectedLength);
            var resource = new TextFileResource("TestResource", fileName);
            // Act
            long actualLength = resource.GetLength(mockFileSystem.Object);
            // Assert
            Assert.That(actualLength, Is.EqualTo(expectedLength));
            mockFileSystem.Verify(fs => fs.GetLength(fileName), Times.Once);
        }

        /// <summary>
        /// Tests that GetLength throws NullReferenceException when fileSystem parameter is null.
        /// </summary>
        [Test]
        public void GetLength_NullFileSystem_ThrowsNullReferenceException()
        {
            // Arrange
            var resource = new TextFileResource("TestResource", "test.txt");
            // Act & Assert
            Assert.Throws<NullReferenceException>(() => resource.GetLength(null!));
        }

        /// <summary>
        /// Tests that GetLength handles empty file name string.
        /// </summary>
        [Test]
        public void GetLength_EmptyFileName_CallsFileSystemWithEmptyString()
        {
            // Arrange
            var mockFileSystem = new Mock<IFileSystem>();
            mockFileSystem.Setup(fs => fs.GetLength(string.Empty)).Returns(0L);
            var resource = new TextFileResource("TestResource", string.Empty);
            // Act
            long actualLength = resource.GetLength(mockFileSystem.Object);
            // Assert
            Assert.That(actualLength, Is.Zero);
            mockFileSystem.Verify(fs => fs.GetLength(string.Empty), Times.Once);
        }

        /// <summary>
        /// Tests that GetLength returns zero for zero-length files.
        /// </summary>
        [Test]
        public void GetLength_ZeroLengthFile_ReturnsZero()
        {
            // Arrange
            var mockFileSystem = new Mock<IFileSystem>();
            mockFileSystem.Setup(fs => fs.GetLength("empty.txt")).Returns(0L);
            var resource = new TextFileResource("TestResource", "empty.txt");
            // Act
            long actualLength = resource.GetLength(mockFileSystem.Object);
            // Assert
            Assert.That(actualLength, Is.Zero);
        }

        /// <summary>
        /// Tests that GetLength correctly handles maximum long value for very large files.
        /// </summary>
        [Test]
        public void GetLength_MaximumFileSize_ReturnsMaxValue()
        {
            // Arrange
            var mockFileSystem = new Mock<IFileSystem>();
            mockFileSystem.Setup(fs => fs.GetLength("huge.bin")).Returns(long.MaxValue);
            var resource = new TextFileResource("TestResource", "huge.bin");
            // Act
            long actualLength = resource.GetLength(mockFileSystem.Object);
            // Assert
            Assert.That(actualLength, Is.EqualTo(long.MaxValue));
        }

        /// <summary>
        /// Tests that GetLength handles negative return values from the file system (edge case).
        /// </summary>
        [Test]
        public void GetLength_NegativeLength_ReturnsNegativeValue()
        {
            // Arrange
            var mockFileSystem = new Mock<IFileSystem>();
            mockFileSystem.Setup(fs => fs.GetLength("invalid.txt")).Returns(-1L);
            var resource = new TextFileResource("TestResource", "invalid.txt");
            // Act
            long actualLength = resource.GetLength(mockFileSystem.Object);
            // Assert
            Assert.That(actualLength, Is.EqualTo(-1L));
        }

        /// <summary>
        /// Tests that GetLength correctly passes the FileName property to the file system.
        /// </summary>
        [Test]
        public void GetLength_DifferentFileNames_PassesCorrectFileNameToFileSystem()
        {
            // Arrange
            const string expectedFileName = "specific-file.txt";
            var mockFileSystem = new Mock<IFileSystem>();
            mockFileSystem.Setup(fs => fs.GetLength(expectedFileName)).Returns(500L);
            var resource = new TextFileResource("TestResource", expectedFileName);
            // Act
            resource.GetLength(mockFileSystem.Object);
            // Assert
            mockFileSystem.Verify(fs => fs.GetLength(expectedFileName), Times.Once);
        }

        /// <summary>
        /// Tests that GetLength returns the correct file length from the file system
        /// when provided with a valid file name and file system.
        /// </summary>
        [TestCase(0L)]
        [TestCase(1L)]
        [TestCase(100L)]
        [TestCase(1024L)]
        [TestCase(1048576L)]
        [TestCase(long.MaxValue)]
        public void GetLength_ValidFileSystem_ReturnsExpectedLength(long expectedLength)
        {
            // Arrange
            const string resourceName = "Test.Resource";
            const string fileName = "test.txt";
            var mockFileSystem = new Mock<IFileSystem>();
            mockFileSystem.Setup(fs => fs.GetLength(fileName)).Returns(expectedLength);
            var resource = new TextFileResource(resourceName, fileName);
            // Act
            long actualLength = resource.GetLength(mockFileSystem.Object);
            // Assert
            Assert.That(actualLength, Is.EqualTo(expectedLength));
            mockFileSystem.Verify(fs => fs.GetLength(fileName), Times.Once);
        }

        /// <summary>
        /// Tests that GetLength passes the correct FileName to the file system's GetLength method.
        /// </summary>
        [TestCase("simple.txt")]
        [TestCase("path/to/file.txt")]
        [TestCase("C:\\absolute\\path\\file.txt")]
        [TestCase("")]
        [TestCase("file with spaces.txt")]
        [TestCase("file_with_special_chars!@#.txt")]
        public void GetLength_VariousFileNames_PassesCorrectFileNameToFileSystem(string fileName)
        {
            // Arrange
            const string resourceName = "Test.Resource";
            const long expectedLength = 42L;
            var mockFileSystem = new Mock<IFileSystem>();
            mockFileSystem.Setup(fs => fs.GetLength(fileName)).Returns(expectedLength);
            var resource = new TextFileResource(resourceName, fileName);
            // Act
            long actualLength = resource.GetLength(mockFileSystem.Object);
            // Assert
            Assert.That(actualLength, Is.EqualTo(expectedLength));
            mockFileSystem.Verify(fs => fs.GetLength(fileName), Times.Once);
        }

        /// <summary>
        /// Tests that GetLength propagates exceptions thrown by the file system's GetLength method.
        /// </summary>
        [Test]
        public void GetLength_FileSystemThrowsIOException_PropagatesException()
        {
            // Arrange
            const string resourceName = "Test.Resource";
            const string fileName = "nonexistent.txt";
            var mockFileSystem = new Mock<IFileSystem>();
            var expectedException = new IOException("File not found");
            mockFileSystem.Setup(fs => fs.GetLength(fileName)).Throws(expectedException);
            var resource = new TextFileResource(resourceName, fileName);
            // Act & Assert
            IOException thrownException = Assert.Throws<IOException>(() => resource.GetLength(mockFileSystem.Object));
            Assert.That(thrownException.Message, Is.EqualTo("File not found"));
        }

        /// <summary>
        /// Tests that GetLength propagates ArgumentException when the file system throws it.
        /// </summary>
        [Test]
        public void GetLength_FileSystemThrowsArgumentException_PropagatesException()
        {
            // Arrange
            const string resourceName = "Test.Resource";
            const string fileName = "invalid:filename.txt";
            var mockFileSystem = new Mock<IFileSystem>();
            var expectedException = new ArgumentException("Invalid file name");
            mockFileSystem.Setup(fs => fs.GetLength(fileName)).Throws(expectedException);
            var resource = new TextFileResource(resourceName, fileName);
            // Act & Assert
            ArgumentException thrownException = Assert.Throws<ArgumentException>(() => resource.GetLength(mockFileSystem.Object));
            Assert.That(thrownException.Message, Is.EqualTo("Invalid file name"));
        }

        /// <summary>
        /// Tests that GetLength returns zero when the file system reports a zero-length file.
        /// </summary>
        [Test]
        public void GetLength_EmptyFile_ReturnsZero()
        {
            // Arrange
            const string resourceName = "Test.Resource";
            const string fileName = "empty.txt";
            var mockFileSystem = new Mock<IFileSystem>();
            mockFileSystem.Setup(fs => fs.GetLength(fileName)).Returns(0L);
            var resource = new TextFileResource(resourceName, fileName);
            // Act
            long actualLength = resource.GetLength(mockFileSystem.Object);
            // Assert
            Assert.That(actualLength, Is.Zero);
        }
    }
}