diff --git a/src/DemaConsulting.FileAssert/Modeling/FileAssertFile.cs b/src/DemaConsulting.FileAssert/Modeling/FileAssertFile.cs
index c474b89..aa78040 100644
--- a/src/DemaConsulting.FileAssert/Modeling/FileAssertFile.cs
+++ b/src/DemaConsulting.FileAssert/Modeling/FileAssertFile.cs
@@ -39,13 +39,7 @@ internal sealed class FileAssertFile
     /// <param name="count">The exact number of files that must match, or null for no constraint.</param>
     /// <param name="minSize">The minimum file size in bytes, or null for no constraint.</param>
     /// <param name="maxSize">The maximum file size in bytes, or null for no constraint.</param>
-    /// <param name="textAssert">The text assert unit, or null when no text: block is declared.</param>
-    /// <param name="pdfAssert">The PDF assert unit, or null when no pdf: block is declared.</param>
-    /// <param name="xmlAssert">The XML assert unit, or null when no xml: block is declared.</param>
-    /// <param name="htmlAssert">The HTML assert unit, or null when no html: block is declared.</param>
-    /// <param name="yamlAssert">The YAML assert unit, or null when no yaml: block is declared.</param>
-    /// <param name="jsonAssert">The JSON assert unit, or null when no json: block is declared.</param>
-    /// <param name="zipAssert">The zip assert unit, or null when no zip: block is declared.</param>
+    /// <param name="asserts">The file-type assert units, each null when the corresponding block is not declared.</param>
     private FileAssertFile(
         string pattern,
         int? min,
@@ -53,13 +47,7 @@ private FileAssertFile(
         int? count,
         long? minSize,
         long? maxSize,
-        FileAssertTextAssert? textAssert,
-        FileAssertPdfAssert? pdfAssert,
-        FileAssertXmlAssert? xmlAssert,
-        FileAssertHtmlAssert? htmlAssert,
-        FileAssertYamlAssert? yamlAssert,
-        FileAssertJsonAssert? jsonAssert,
-        FileAssertZipAssert? zipAssert)
+        FileTypeAsserts asserts)
     {
         // Store all validated properties for use during execution
         Pattern = pattern;
@@ -68,15 +56,35 @@ private FileAssertFile(
         Count = count;
         MinSize = minSize;
         MaxSize = maxSize;
-        TextAssert = textAssert;
-        PdfAssert = pdfAssert;
-        XmlAssert = xmlAssert;
-        HtmlAssert = htmlAssert;
-        YamlAssert = yamlAssert;
-        JsonAssert = jsonAssert;
-        ZipAssert = zipAssert;
+        TextAssert = asserts.TextAssert;
+        PdfAssert = asserts.PdfAssert;
+        XmlAssert = asserts.XmlAssert;
+        HtmlAssert = asserts.HtmlAssert;
+        YamlAssert = asserts.YamlAssert;
+        JsonAssert = asserts.JsonAssert;
+        ZipAssert = asserts.ZipAssert;
     }
 
+    /// <summary>
+    ///     Groups the optional file-type assert units so they can be passed to the
+    ///     <see cref="FileAssertFile"/> constructor as a single parameter.
+    /// </summary>
+    /// <param name="TextAssert">The text assert unit, or null when no text: block is declared.</param>
+    /// <param name="PdfAssert">The PDF assert unit, or null when no pdf: block is declared.</param>
+    /// <param name="XmlAssert">The XML assert unit, or null when no xml: block is declared.</param>
+    /// <param name="HtmlAssert">The HTML assert unit, or null when no html: block is declared.</param>
+    /// <param name="YamlAssert">The YAML assert unit, or null when no yaml: block is declared.</param>
+    /// <param name="JsonAssert">The JSON assert unit, or null when no json: block is declared.</param>
+    /// <param name="ZipAssert">The zip assert unit, or null when no zip: block is declared.</param>
+    private readonly record struct FileTypeAsserts(
+        FileAssertTextAssert? TextAssert,
+        FileAssertPdfAssert? PdfAssert,
+        FileAssertXmlAssert? XmlAssert,
+        FileAssertHtmlAssert? HtmlAssert,
+        FileAssertYamlAssert? YamlAssert,
+        FileAssertJsonAssert? JsonAssert,
+        FileAssertZipAssert? ZipAssert);
+
     /// <summary>
     ///     Gets the glob pattern used to match files.
     /// </summary>
@@ -172,7 +180,7 @@ internal static FileAssertFile Create(FileAssertFileData data)
         // Return the fully constructed file assertion
         return new FileAssertFile(
             data.Pattern, data.Min, data.Max, data.Count, data.MinSize, data.MaxSize,
-            textAssert, pdfAssert, xmlAssert, htmlAssert, yamlAssert, jsonAssert, zipAssert);
+            new FileTypeAsserts(textAssert, pdfAssert, xmlAssert, htmlAssert, yamlAssert, jsonAssert, zipAssert));
     }
 
     /// <summary>
diff --git a/src/DemaConsulting.FileAssert/Modeling/FileAssertPdfAssert.cs b/src/DemaConsulting.FileAssert/Modeling/FileAssertPdfAssert.cs
index 113af30..21009c0 100644
--- a/src/DemaConsulting.FileAssert/Modeling/FileAssertPdfAssert.cs
+++ b/src/DemaConsulting.FileAssert/Modeling/FileAssertPdfAssert.cs
@@ -316,7 +316,8 @@ private void RunDocumentAssertions(IContext context, string displayPath, PdfDocu
         }
         else
         {
-            _pages?.Apply(context, displayPath, document.GetPages().Count());
+            // When we reach here _text is empty, so the guard above guarantees _pages is non-null
+            _pages!.Apply(context, displayPath, document.GetPages().Count());
         }
     }
 
@@ -326,7 +327,7 @@ private void RunDocumentAssertions(IContext context, string displayPath, PdfDocu
     /// </summary>
     /// <param name="pages">The ordered list of pages from the PDF document.</param>
     /// <returns>A single string containing all page text joined with newline separators.</returns>
-    private static string BuildPageText(IReadOnlyList<Page> pages)
+    private static string BuildPageText(List<Page> pages)
     {
         var sb = new StringBuilder();
         for (var i = 0; i < pages.Count; i++)
diff --git a/src/DemaConsulting.FileAssert/SelfTest/ValidationPdf.cs b/src/DemaConsulting.FileAssert/SelfTest/ValidationPdf.cs
index 845bdfe..7f36047 100644
--- a/src/DemaConsulting.FileAssert/SelfTest/ValidationPdf.cs
+++ b/src/DemaConsulting.FileAssert/SelfTest/ValidationPdf.cs
@@ -49,7 +49,7 @@ private static void RunPdfTest(Context context, DemaConsulting.TestResults.TestR
             var configFile = tempDir.GetFilePath(".fileassert.yaml");
 
             // Build a minimal PDF in memory using PdfPig's writer API
-            var builder = new PdfDocumentBuilder();
+            using var builder = new PdfDocumentBuilder();
             builder.DocumentInformation.Title = "Test PDF";
             var font = builder.AddStandard14Font(Standard14Font.Helvetica);
             var page = builder.AddPage(PageSize.A4);
diff --git a/test/DemaConsulting.FileAssert.Tests/Cli/ContextNewPropertiesTests.cs b/test/DemaConsulting.FileAssert.Tests/Cli/ContextNewPropertiesTests.cs
index 38aa754..b8f1141 100644
--- a/test/DemaConsulting.FileAssert.Tests/Cli/ContextNewPropertiesTests.cs
+++ b/test/DemaConsulting.FileAssert.Tests/Cli/ContextNewPropertiesTests.cs
@@ -94,8 +94,8 @@ public void Context_Create_MixedArguments_ParsesCorrectly()
         // Assert
         Assert.True(context.Silent);
         Assert.Equal("cfg.yaml", context.ConfigFile);
-        Assert.Single(context.Filters);
-        Assert.Equal("my-filter", context.Filters[0]);
+        var filter = Assert.Single(context.Filters);
+        Assert.Equal("my-filter", filter);
     }
 
     /// <summary>
diff --git a/test/DemaConsulting.FileAssert.Tests/Configuration/ConfigurationTests.cs b/test/DemaConsulting.FileAssert.Tests/Configuration/ConfigurationTests.cs
index a840e2b..835e710 100644
--- a/test/DemaConsulting.FileAssert.Tests/Configuration/ConfigurationTests.cs
+++ b/test/DemaConsulting.FileAssert.Tests/Configuration/ConfigurationTests.cs
@@ -57,13 +57,11 @@ public void Configuration_LoadYaml_BuildsCompleteTestHierarchy()
         var config = FileAssertConfig.ReadFromFile(configPath);
 
         // Assert - the full hierarchy is correctly constructed
-        Assert.Single(config.Tests);
-        var test = config.Tests[0];
+        var test = Assert.Single(config.Tests);
         Assert.Equal("License Check", test.Name);
-        Assert.Single(test.Tags);
-        Assert.Equal("license", test.Tags[0]);
-        Assert.Single(test.Files);
-        var file = test.Files[0];
+        var tag = Assert.Single(test.Tags);
+        Assert.Equal("license", tag);
+        var file = Assert.Single(test.Files);
         Assert.Equal("**/*.txt", file.Pattern);
         Assert.Equal(1, file.Min);
         Assert.Single(file.TextAssert!.Rules);
diff --git a/test/DemaConsulting.FileAssert.Tests/Configuration/FileAssertConfigTests.cs b/test/DemaConsulting.FileAssert.Tests/Configuration/FileAssertConfigTests.cs
index 4d0c60c..855dcb8 100644
--- a/test/DemaConsulting.FileAssert.Tests/Configuration/FileAssertConfigTests.cs
+++ b/test/DemaConsulting.FileAssert.Tests/Configuration/FileAssertConfigTests.cs
@@ -64,8 +64,8 @@ public void FileAssertConfig_ReadFromFile_ValidFile_ReturnsConfig()
         var config = FileAssertConfig.ReadFromFile(configPath);
 
         // Assert
-        Assert.Single(config.Tests);
-        Assert.Equal("Sample Test", config.Tests[0].Name);
+        var test = Assert.Single(config.Tests);
+        Assert.Equal("Sample Test", test.Name);
 
     }
 
@@ -285,11 +285,9 @@ public void FileAssertConfig_ReadFromFile_PdfAssertConfig_ParsesCorrectly()
         var config = FileAssertConfig.ReadFromFile(configPath);
 
         // Assert - one test was parsed with one file assertion and populated PDF settings
-        Assert.Single(config.Tests);
-        Assert.Equal("PDF Check", config.Tests[0].Name);
-        Assert.Single(config.Tests[0].Files);
-
-        var fileAssertion = config.Tests[0].Files[0];
+        var test = Assert.Single(config.Tests);
+        Assert.Equal("PDF Check", test.Name);
+        var fileAssertion = Assert.Single(test.Files);
         Assert.Equal("report.pdf", fileAssertion.Pattern);
         Assert.NotNull(fileAssertion.PdfAssert);
 
diff --git a/test/DemaConsulting.FileAssert.Tests/Modeling/FileAssertHtmlAssertTests.cs b/test/DemaConsulting.FileAssert.Tests/Modeling/FileAssertHtmlAssertTests.cs
index a6e948a..0d06859 100644
--- a/test/DemaConsulting.FileAssert.Tests/Modeling/FileAssertHtmlAssertTests.cs
+++ b/test/DemaConsulting.FileAssert.Tests/Modeling/FileAssertHtmlAssertTests.cs
@@ -460,8 +460,8 @@ public void FileAssertHtmlAssert_Run_UnauthorizedAccess_WritesError()
         htmlAssert.Run(context, container, "page.html");
 
         // Assert: the IO failure is reported
-        Assert.Single(context.Errors);
-        Assert.Contains("could not be parsed as an HTML document", context.Errors[0]);
+        var error = Assert.Single(context.Errors);
+        Assert.Contains("could not be parsed as an HTML document", error);
     }
 
     /// <summary>
diff --git a/test/DemaConsulting.FileAssert.Tests/Modeling/FileAssertJsonAssertTests.cs b/test/DemaConsulting.FileAssert.Tests/Modeling/FileAssertJsonAssertTests.cs
index 4e74505..f088e47 100644
--- a/test/DemaConsulting.FileAssert.Tests/Modeling/FileAssertJsonAssertTests.cs
+++ b/test/DemaConsulting.FileAssert.Tests/Modeling/FileAssertJsonAssertTests.cs
@@ -364,8 +364,8 @@ public void FileAssertJsonAssert_Run_InvalidJson_WritesParseError()
             jsonAssert.Run(context, container, fileName);
 
             // Assert: the error identifies a parse failure, not an IO failure
-            Assert.Single(context.Errors);
-            Assert.Contains("could not be parsed as a JSON document", context.Errors[0]);
+            var error = Assert.Single(context.Errors);
+            Assert.Contains("could not be parsed as a JSON document", error);
         }
         finally
         {
@@ -389,8 +389,8 @@ public void FileAssertJsonAssert_Run_IOError_WritesReadError()
         jsonAssert.Run(context, container, "data.json");
 
         // Assert: the error identifies an IO failure, not a parse failure
-        Assert.Single(context.Errors);
-        Assert.Contains("could not be read", context.Errors[0]);
+        var error = Assert.Single(context.Errors);
+        Assert.Contains("could not be read", error);
     }
 
     /// <summary>
diff --git a/test/DemaConsulting.FileAssert.Tests/Modeling/FileAssertRuleTests.cs b/test/DemaConsulting.FileAssert.Tests/Modeling/FileAssertRuleTests.cs
index 6a31bf1..aa47cec 100644
--- a/test/DemaConsulting.FileAssert.Tests/Modeling/FileAssertRuleTests.cs
+++ b/test/DemaConsulting.FileAssert.Tests/Modeling/FileAssertRuleTests.cs
@@ -43,8 +43,8 @@ public void FileAssertRule_Create_WithContains_ReturnsContainsRule()
         var rule = FileAssertRule.Create(data);
 
         // Assert
-        Assert.IsType<FileAssertContainsRule>(rule);
-        Assert.Equal("expected text", ((FileAssertContainsRule)rule).Value);
+        var containsRule = Assert.IsType<FileAssertContainsRule>(rule);
+        Assert.Equal("expected text", containsRule.Value);
     }
 
     /// <summary>
@@ -60,8 +60,8 @@ public void FileAssertRule_Create_WithMatches_ReturnsMatchesRule()
         var rule = FileAssertRule.Create(data);
 
         // Assert
-        Assert.IsType<FileAssertMatchesRule>(rule);
-        Assert.Equal(@"\d+", ((FileAssertMatchesRule)rule).Pattern);
+        var matchesRule = Assert.IsType<FileAssertMatchesRule>(rule);
+        Assert.Equal(@"\d+", matchesRule.Pattern);
     }
 
     /// <summary>
@@ -172,8 +172,8 @@ public void FileAssertRule_Create_WithDoesNotContain_ReturnsDoesNotContainRule()
         var rule = FileAssertRule.Create(data);
 
         // Assert
-        Assert.IsType<FileAssertDoesNotContainRule>(rule);
-        Assert.Equal("forbidden text", ((FileAssertDoesNotContainRule)rule).Value);
+        var doesNotContainRule = Assert.IsType<FileAssertDoesNotContainRule>(rule);
+        Assert.Equal("forbidden text", doesNotContainRule.Value);
     }
 
     /// <summary>
@@ -189,8 +189,8 @@ public void FileAssertRule_Create_WithDoesNotContainRegex_ReturnsDoesNotMatchRul
         var rule = FileAssertRule.Create(data);
 
         // Assert
-        Assert.IsType<FileAssertDoesNotMatchRule>(rule);
-        Assert.Equal(@"FATAL|ERROR", ((FileAssertDoesNotMatchRule)rule).Pattern);
+        var doesNotMatchRule = Assert.IsType<FileAssertDoesNotMatchRule>(rule);
+        Assert.Equal(@"FATAL|ERROR", doesNotMatchRule.Pattern);
     }
 
     /// <summary>
diff --git a/test/DemaConsulting.FileAssert.Tests/Modeling/FileAssertYamlAssertTests.cs b/test/DemaConsulting.FileAssert.Tests/Modeling/FileAssertYamlAssertTests.cs
index fd2deac..93c1d91 100644
--- a/test/DemaConsulting.FileAssert.Tests/Modeling/FileAssertYamlAssertTests.cs
+++ b/test/DemaConsulting.FileAssert.Tests/Modeling/FileAssertYamlAssertTests.cs
@@ -438,8 +438,8 @@ public void FileAssertYamlAssert_Run_InvalidFile_RemainingAssertionsSkipped()
             yamlAssert.Run(context, container, fileName);
 
             // Assert - exactly one error (the parse failure); the queries are not evaluated
-            Assert.Single(context.Errors);
-            Assert.Contains("could not be parsed", context.Errors[0]);
+            var error = Assert.Single(context.Errors);
+            Assert.Contains("could not be parsed", error);
         }
         finally
         {
diff --git a/test/DemaConsulting.FileAssert.Tests/Modeling/FileAssertZipAssertTests.cs b/test/DemaConsulting.FileAssert.Tests/Modeling/FileAssertZipAssertTests.cs
index 883b0b6..8838afe 100644
--- a/test/DemaConsulting.FileAssert.Tests/Modeling/FileAssertZipAssertTests.cs
+++ b/test/DemaConsulting.FileAssert.Tests/Modeling/FileAssertZipAssertTests.cs
@@ -20,6 +20,7 @@
 
 using System.Collections.ObjectModel;
 using System.IO.Compression;
+using System.Linq;
 using DemaConsulting.FileAssert.Cli;
 using DemaConsulting.FileAssert.Configuration;
 using DemaConsulting.FileAssert.Modeling;
@@ -82,12 +83,13 @@ private static void CreateZipFile(string path, IEnumerable<string> entries)
         File.Delete(path);
 
         using var archive = ZipFile.Open(path, ZipArchiveMode.Create);
-        foreach (var entry in entries)
+        foreach (var stream in entries.Select(entry => archive.CreateEntry(entry).Open()))
         {
-            using var stream = archive.CreateEntry(entry).Open();
-
-            // Write a single placeholder byte so the entry is not an empty-stream edge case
-            stream.WriteByte(0x00);
+            using (stream)
+            {
+                // Write a single placeholder byte so the entry is not an empty-stream edge case
+                stream.WriteByte(0x00);
+            }
         }
     }
 
@@ -238,10 +240,10 @@ public void FileAssertZipAssert_Create_ValidData_CreatesZipAssert()
 
         // Assert
         Assert.NotNull(zipAssert);
-        Assert.Single(zipAssert.Files);
-        Assert.Equal("lib/**/*.dll", zipAssert.Files[0].Pattern);
-        Assert.Equal(1, zipAssert.Files[0].Min);
-        Assert.Null(zipAssert.Files[0].Max);
+        var file = Assert.Single(zipAssert.Files);
+        Assert.Equal("lib/**/*.dll", file.Pattern);
+        Assert.Equal(1, file.Min);
+        Assert.Null(file.Max);
     }
 
     /// <summary>