Add unit tests for handling invalid LiteDB files

LiteDB.Tests/Database/InvalidFile_Tests.cs

@@ -0,0 +1,126 @@
+using System;
+using System.IO;
+using System.Linq;
+using System.Collections.Generic;
+using FluentAssertions;
+using Xunit;
+
+namespace LiteDB.Tests.Database
+{
+    public class InvalidFile_Tests
+    {
+        [Fact]
+        public void Test_AddDatabase_InvalidDatabase()
+        {
+            // Set the database name and file name
+            string dbName = "invalidDb";
+            string fileName = $"{dbName}.db";
+
+            // Create an invalid LiteDB database file for testing
+            File.WriteAllText(fileName, "Invalid content");
+
+            // Verify the file exists and content is correct
+            Assert.True(File.Exists(fileName));
+            Assert.Equal("Invalid content", File.ReadAllText(fileName));
+
+            // Act & Assert: Try to open the invalid database and expect an exception
+            Assert.Throws<LiteException>(() =>
+            {
+                using (var db = new LiteDatabase(fileName))
+                {
+                    // Attempt to perform an operation to ensure the database file is read
+                    var col = db.GetCollection("test");
+                    col.Insert(new BsonDocument { ["name"] = "test" });
+                }
+            });
+
+            // Clean up: Remove the invalid database file after the test
+            if (File.Exists(fileName))
+            {
+                File.Delete(fileName);
+            }
+        }
+
+        [Fact]
+        public void Test_AddDatabase_InvalidDatabase_LargeFile()
+        {
+            // Set the database name and file name
+            string dbName = "largeInvalidDb";
+            string fileName = $"{dbName}.db";
+
+            // Create an invalid LiteDB database file with content larger than 16KB for testing
+            string invalidContent = new string('a', 16 * 1024 + 1);
+            File.WriteAllText(fileName, invalidContent);
+
+            // Verify the file exists and content is correct
+            Assert.True(File.Exists(fileName));
+            Assert.Equal(invalidContent, File.ReadAllText(fileName));
+
+            // Act & Assert: Try to open the invalid database and expect an exception
+            Assert.Throws<LiteException>(() =>
+            {
+                using (var db = new LiteDatabase(fileName))
+                {
+                    // Attempt to perform an operation to ensure the database file is read
+                    var col = db.GetCollection("test");
+                    col.Insert(new BsonDocument { ["name"] = "test" });
+                }
+            });
+
+            // Clean up: Remove the invalid database file after the test
+            if (File.Exists(fileName))
+            {
+                File.Delete(fileName);
+            }
+        }
+
+        [Fact]
+        public void Test_AddDatabase_InvalidDatabase_MemoryStream()
+        {
+            // Create an invalid LiteDB database content
+            byte[] invalidContent = System.Text.Encoding.UTF8.GetBytes("Invalid content");
+
+            using (var stream = new MemoryStream(invalidContent))
+            {
+                // Act & Assert: Try to open the invalid database and expect an exception
+                Exception ex = Record.Exception(() =>
+                {
+                    using (var db = new LiteDatabase(stream))
+                    {
+                        // Attempt to perform an operation to ensure the database file is read
+                        var col = db.GetCollection("test");
+                        col.Insert(new BsonDocument { ["name"] = "test" });
+                    }
+                });
+
+                Assert.NotNull(ex);
+                Assert.IsType<LiteException>(ex);
+            }
+        }
+
+        [Fact]
+        public void Test_AddDatabase_InvalidDatabase_LargeFile_MemoryStream()
+        {
+            // Create an invalid LiteDB database content larger than 16KB
+            byte[] invalidContent = new byte[16 * 1024 + 1];
+            for (int i = 0; i < invalidContent.Length; i++) invalidContent[i] = (byte)'a';
+
+            using (var stream = new MemoryStream(invalidContent))
+            {
+                // Act & Assert: Try to open the invalid database and expect an exception
+                Exception ex = Record.Exception(() =>
+                {
+                    using (var db = new LiteDatabase(stream))
+                    {
+                        // Attempt to perform an operation to ensure the database file is read
+                        var col = db.GetCollection("test");
+                        col.Insert(new BsonDocument { ["name"] = "test" });
+                    }
+                });
+
+                Assert.NotNull(ex);
+                Assert.IsType<LiteException>(ex);
+            }
+        }
+    }
+}