diff --git a/Sources/JExtractSwiftLib/FFM/FFMSwift2JavaGenerator.swift b/Sources/JExtractSwiftLib/FFM/FFMSwift2JavaGenerator.swift
index 41c063048..64614318d 100644
--- a/Sources/JExtractSwiftLib/FFM/FFMSwift2JavaGenerator.swift
+++ b/Sources/JExtractSwiftLib/FFM/FFMSwift2JavaGenerator.swift
@@ -85,7 +85,7 @@ package class FFMSwift2JavaGenerator: Swift2JavaGenerator {
 
     // If we are forced to write empty files, construct the expected outputs.
     // It is sufficient to use file names only, since SwiftPM requires names to be unique within a module anyway.
-    if translator.config.writeEmptyFiles ?? false {
+    if translator.config.effectiveWriteEmptyFiles {
       self.expectedOutputSwiftFileNames = Set(
         translator.inputs.compactMap { (input) -> String? in
           guard let fileName = input.path.split(separator: PATH_SEPARATOR).last else {
diff --git a/Sources/JExtractSwiftLib/JNI/JNISwift2JavaGenerator+JavaTranslation.swift b/Sources/JExtractSwiftLib/JNI/JNISwift2JavaGenerator+JavaTranslation.swift
index ddb88b9f4..53db4d40d 100644
--- a/Sources/JExtractSwiftLib/JNI/JNISwift2JavaGenerator+JavaTranslation.swift
+++ b/Sources/JExtractSwiftLib/JNI/JNISwift2JavaGenerator+JavaTranslation.swift
@@ -1162,7 +1162,6 @@ extension JNISwift2JavaGenerator {
       genericParameters: [SwiftGenericParameterDeclaration],
       genericRequirements: [SwiftGenericRequirement],
     ) throws -> TranslatedResult {
-      let arity = elements.count
       var outParameters: [OutParameter] = []
       var elementOutParamNames: [String] = []
       var elementConversions: [JavaNativeConversionStep] = []
diff --git a/Sources/JExtractSwiftLib/JNI/JNISwift2JavaGenerator.swift b/Sources/JExtractSwiftLib/JNI/JNISwift2JavaGenerator.swift
index 07b724873..beffe9fb0 100644
--- a/Sources/JExtractSwiftLib/JNI/JNISwift2JavaGenerator.swift
+++ b/Sources/JExtractSwiftLib/JNI/JNISwift2JavaGenerator.swift
@@ -88,7 +88,7 @@ package class JNISwift2JavaGenerator: Swift2JavaGenerator {
 
     // If we are forced to write empty files, construct the expected outputs.
     // It is sufficient to use file names only, since SwiftPM requires names to be unique within a module anyway.
-    if translator.config.writeEmptyFiles ?? false {
+    if translator.config.effectiveWriteEmptyFiles {
       self.expectedOutputSwiftFileNames = Set(
         translator.inputs.compactMap { (input) -> String? in
           guard let fileName = input.path.split(separator: PATH_SEPARATOR).last else {
diff --git a/Sources/SwiftJavaConfigurationShared/Configuration.swift b/Sources/SwiftJavaConfigurationShared/Configuration.swift
index 7eab2fef6..ea5981f21 100644
--- a/Sources/SwiftJavaConfigurationShared/Configuration.swift
+++ b/Sources/SwiftJavaConfigurationShared/Configuration.swift
@@ -49,7 +49,10 @@ public struct Configuration: Codable {
     mode ?? .default
   }
 
-  public var writeEmptyFiles: Bool? // FIXME: default it to false, but that plays not nice with Codable
+  public var writeEmptyFiles: Bool?
+  public var effectiveWriteEmptyFiles: Bool {
+    writeEmptyFiles ?? false
+  }
 
   public var minimumInputAccessLevelMode: JExtractMinimumAccessLevelMode?
   public var effectiveMinimumInputAccessLevelMode: JExtractMinimumAccessLevelMode {
diff --git a/Tests/JExtractSwiftTests/FFMNestedTypesTests.swift b/Tests/JExtractSwiftTests/FFMNestedTypesTests.swift
index 4c5171c5b..1b23d2997 100644
--- a/Tests/JExtractSwiftTests/FFMNestedTypesTests.swift
+++ b/Tests/JExtractSwiftTests/FFMNestedTypesTests.swift
@@ -37,7 +37,7 @@ final class FFMNestedTypesTests {
 
     try st.analyze(path: "Fake.swift", text: class_interfaceFile)
 
-    let generator = FFMSwift2JavaGenerator(
+    let _ = FFMSwift2JavaGenerator(
       config: config,
       translator: st,
       javaPackage: "com.example.swift",
@@ -45,10 +45,6 @@ final class FFMNestedTypesTests {
       javaOutputDirectory: "/fake"
     )
 
-    guard let ty = st.importedTypes["MyNamespace.MyNestedStruct"] else {
-      fatalError("Didn't import nested type!")
-    }
-
+    #expect(st.importedTypes["MyNamespace.MyNestedStruct"] != nil, "Didn't import nested type!")
   }
-
 }
diff --git a/Tests/JExtractSwiftTests/MethodImportTests.swift b/Tests/JExtractSwiftTests/MethodImportTests.swift
index aa546f3d9..9d723c3fb 100644
--- a/Tests/JExtractSwiftTests/MethodImportTests.swift
+++ b/Tests/JExtractSwiftTests/MethodImportTests.swift
@@ -83,7 +83,7 @@ final class MethodImportTests {
       javaOutputDirectory: "/fake"
     )
 
-    let funcDecl = st.importedGlobalFuncs.first { $0.name == "helloWorld" }!
+    let funcDecl = try #require(st.importedGlobalFuncs.first { $0.name == "helloWorld" })
 
     let output = CodePrinter.toString { printer in
       generator.printJavaBindingWrapperMethod(&printer, funcDecl)
@@ -117,9 +117,11 @@ final class MethodImportTests {
 
     try st.analyze(path: "Fake.swift", text: class_interfaceFile)
 
-    let funcDecl = st.importedGlobalFuncs.first {
-      $0.name == "globalTakeInt"
-    }!
+    let funcDecl = try #require(
+      st.importedGlobalFuncs.first {
+        $0.name == "globalTakeInt"
+      }
+    )
 
     let generator = FFMSwift2JavaGenerator(
       config: config,
@@ -164,9 +166,11 @@ final class MethodImportTests {
 
     try st.analyze(path: "Fake.swift", text: class_interfaceFile)
 
-    let funcDecl = st.importedGlobalFuncs.first {
-      $0.name == "globalTakeIntLongString"
-    }!
+    let funcDecl = try #require(
+      st.importedGlobalFuncs.first {
+        $0.name == "globalTakeIntLongString"
+      }
+    )
 
     let generator = FFMSwift2JavaGenerator(
       config: config,
@@ -208,9 +212,11 @@ final class MethodImportTests {
 
     try st.analyze(path: "Fake.swift", text: class_interfaceFile)
 
-    let funcDecl = st.importedGlobalFuncs.first {
-      $0.name == "globalReturnClass"
-    }!
+    let funcDecl = try #require(
+      st.importedGlobalFuncs.first {
+        $0.name == "globalReturnClass"
+      }
+    )
 
     let generator = FFMSwift2JavaGenerator(
       config: config,
@@ -252,9 +258,11 @@ final class MethodImportTests {
 
     try st.analyze(path: "Fake.swift", text: class_interfaceFile)
 
-    let funcDecl = st.importedGlobalFuncs.first {
-      $0.name == "swapRawBufferPointer"
-    }!
+    let funcDecl = try #require(
+      st.importedGlobalFuncs.first {
+        $0.name == "swapRawBufferPointer"
+      }
+    )
 
     let generator = FFMSwift2JavaGenerator(
       config: config,
@@ -299,9 +307,11 @@ final class MethodImportTests {
 
     try st.analyze(path: "Fake.swift", text: class_interfaceFile)
 
-    let funcDecl: ImportedFunc = st.importedTypes["MySwiftClass"]!.methods.first {
-      $0.name == "helloMemberFunction"
-    }!
+    let funcDecl: ImportedFunc = try #require(
+      st.importedTypes["MySwiftClass"]!.methods.first {
+        $0.name == "helloMemberFunction"
+      }
+    )
 
     let generator = FFMSwift2JavaGenerator(
       config: config,
@@ -342,9 +352,11 @@ final class MethodImportTests {
 
     try st.analyze(path: "Fake.swift", text: class_interfaceFile)
 
-    let funcDecl: ImportedFunc = st.importedTypes["MySwiftClass"]!.methods.first {
-      $0.name == "makeInt"
-    }!
+    let funcDecl: ImportedFunc = try #require(
+      st.importedTypes["MySwiftClass"]!.methods.first {
+        $0.name == "makeInt"
+      }
+    )
 
     let generator = FFMSwift2JavaGenerator(
       config: config,
@@ -391,9 +403,11 @@ final class MethodImportTests {
 
     try st.analyze(path: "Fake.swift", text: class_interfaceFile)
 
-    let initDecl: ImportedFunc = st.importedTypes["MySwiftClass"]!.initializers.first {
-      $0.name == "init"
-    }!
+    let initDecl: ImportedFunc = try #require(
+      st.importedTypes["MySwiftClass"]!.initializers.first {
+        $0.name == "init"
+      }
+    )
 
     let generator = FFMSwift2JavaGenerator(
       config: config,
@@ -444,9 +458,11 @@ final class MethodImportTests {
 
     try st.analyze(path: "Fake.swift", text: class_interfaceFile)
 
-    let initDecl: ImportedFunc = st.importedTypes["MySwiftStruct"]!.initializers.first {
-      $0.name == "init"
-    }!
+    let initDecl: ImportedFunc = try #require(
+      st.importedTypes["MySwiftStruct"]!.initializers.first {
+        $0.name == "init"
+      }
+    )
 
     let generator = FFMSwift2JavaGenerator(
       config: config,
diff --git a/Tests/SwiftJavaConfigurationSharedTests/SwiftJavaConfigurationTests.swift b/Tests/SwiftJavaConfigurationSharedTests/SwiftJavaConfigurationTests.swift
index 4dbea421d..eb8c2dd4e 100644
--- a/Tests/SwiftJavaConfigurationSharedTests/SwiftJavaConfigurationTests.swift
+++ b/Tests/SwiftJavaConfigurationSharedTests/SwiftJavaConfigurationTests.swift
@@ -20,7 +20,7 @@ struct SwiftJavaConfigurationTests {
 
   @Test
   func parseJSONWithComments() throws {
-    let config = try readConfiguration(
+    let _ = try readConfiguration(
       string:
         """
         // some comments