fix: enforce non-null user preference optionals

src/main/java/com/krotname/javasoundrecorder/config/UserPreferences.java

@@ -2,6 +2,7 @@
 
 import java.nio.file.Path;
 import java.time.Duration;
+import java.util.Objects;
 import java.util.Optional;
 
 public record UserPreferences(
@@ -10,10 +11,10 @@ public record UserPreferences(
         Optional<Boolean> uploadEnabled,
         Optional<String> audioInputName) {
     public UserPreferences {
-        recordingDuration = recordingDuration == null ? Optional.empty() : recordingDuration;
-        recordingDirectory = recordingDirectory == null ? Optional.empty() : recordingDirectory;
-        uploadEnabled = uploadEnabled == null ? Optional.empty() : uploadEnabled;
-        audioInputName = audioInputName == null ? Optional.empty() : audioInputName.map(String::trim)
+        recordingDuration = Objects.requireNonNull(recordingDuration, "recordingDuration");
+        recordingDirectory = Objects.requireNonNull(recordingDirectory, "recordingDirectory");
+        uploadEnabled = Objects.requireNonNull(uploadEnabled, "uploadEnabled");
+        audioInputName = Objects.requireNonNull(audioInputName, "audioInputName").map(String::trim)
                 .filter(value -> !value.isEmpty());
     }
 

src/test/java/com/krotname/javasoundrecorder/config/UserPreferencesTest.java

@@ -0,0 +1,40 @@
+package com.krotname.javasoundrecorder.config;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+import java.util.Optional;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.function.Executable;
+
+class UserPreferencesTest {
+    @Test
+    void rejectsNullRecordingDuration() {
+        assertNullComponent("recordingDuration",
+                () -> new UserPreferences(null, Optional.empty(), Optional.empty(), Optional.empty()));
+    }
+
+    @Test
+    void rejectsNullRecordingDirectory() {
+        assertNullComponent("recordingDirectory",
+                () -> new UserPreferences(Optional.empty(), null, Optional.empty(), Optional.empty()));
+    }
+
+    @Test
+    void rejectsNullUploadEnabled() {
+        assertNullComponent("uploadEnabled",
+                () -> new UserPreferences(Optional.empty(), Optional.empty(), null, Optional.empty()));
+    }
+
+    @Test
+    void rejectsNullAudioInputName() {
+        assertNullComponent("audioInputName",
+                () -> new UserPreferences(Optional.empty(), Optional.empty(), Optional.empty(), null));
+    }
+
+    private static void assertNullComponent(String componentName, Executable constructor) {
+        NullPointerException error = assertThrows(NullPointerException.class, constructor);
+
+        assertEquals(componentName, error.getMessage());
+    }
+}