@@ -21,6 +21,7 @@
 import static org.lmdbjava.TargetName.resolveFilename;
 import static org.lmdbjava.TestUtils.invokePrivateConstructor;
 
+import org.assertj.core.api.Assertions;
 import org.junit.jupiter.api.Test;
 
 /** Test {@link TargetName}. */
@@ -66,6 +67,36 @@ void externalTakesPriority() {
     assertThat(isExternal("/lm.so")).isTrue();
   }
 
+  @Test
+  void resolveExtension_null() {
+    assertThat(TargetName.resolveExtension(null)).isEqualTo("so");
+  }
+
+  @Test
+  void resolveExtension_unknown() {
+    assertThat(TargetName.resolveExtension("foo")).isEqualTo("so");
+  }
+
+  @Test
+  void badArch() {
+    Assertions.assertThatThrownBy(
+            () -> {
+              TargetName.resolveFilename(NONE, NONE, "badArch", "Linux");
+            })
+        .isInstanceOf(UnsupportedOperationException.class)
+        .hasMessageContaining("os.arch");
+  }
+
+  @Test
+  void badOs() {
+    Assertions.assertThatThrownBy(
+            () -> {
+              TargetName.resolveFilename(NONE, NONE, "arch", "badOs");
+            })
+        .isInstanceOf(UnsupportedOperationException.class)
+        .hasMessageContaining("os.name");
+  }
+
   private void embed(final String lib, final String arch, final String os) {
     assertThat(resolveFilename(NONE, NONE, arch, os)).isEqualTo("org/lmdbjava/native/" + lib);
     assertThat(isExternal(NONE)).isFalse();