Add CppMainNameProvider test

src/main/java/de/monticore/lang/monticar/emam2wasm/cpp/CppMainNameProvider.java

 package de.monticore.lang.monticar.emam2wasm.cpp;
 
+import static de.monticore.lang.monticar.contract.Precondition.requiresNotNull;
+
 import de.monticore.symboltable.Symbol;
 import org.springframework.stereotype.Component;
 
@@ -10,7 +12,7 @@ public class CppMainNameProvider implements CppNameProvider {
 
   @Override
   public String getName(Symbol model) {
-    return model.getName();
+    return requiresNotNull(model).getName();
   }
 
   @Override

src/test/java/de/monticore/lang/monticar/emam2wasm/cpp/CppMainNameProviderTest.java

+package de.monticore.lang.monticar.emam2wasm.cpp;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatExceptionOfType;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+import de.monticore.lang.monticar.contract.Precondition.PreconditionViolationException;
+import de.monticore.symboltable.Symbol;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Nested;
+import org.junit.jupiter.api.Test;
+
+class CppMainNameProviderTest {
+
+  private static final Symbol NULL_SYMBOL = null;
+  private static final String SOME_SYMBOL_NAME = "someSymbolName";
+  private static final String EXPECTED_SYMBOL_NAME = SOME_SYMBOL_NAME;
+  private static final Path EXPECTED_FILE_PATH = Paths.get("someSymbolName.cpp");
+
+  private CppMainNameProvider nameProvider;
+  private Symbol symbol;
+
+  @BeforeEach
+  void setUp() {
+    nameProvider = new CppMainNameProvider();
+    symbol = mock(Symbol.class);
+    when(symbol.getName()).thenReturn(SOME_SYMBOL_NAME);
+  }
+
+  @Nested
+  class GetName {
+
+    @Nested
+    class ShouldThrowPreconditionViolationException {
+
+      @Test
+      void whenSymbolIsNull() {
+        assertThatExceptionOfType(PreconditionViolationException.class)
+            .isThrownBy(() -> nameProvider.getName(NULL_SYMBOL));
+      }
+    }
+
+    @Nested
+    class ShouldReturnSymbolName {
+
+      @Test
+      void whenSymbolIsNotNull() {
+        assertThat(nameProvider.getName(symbol)).isEqualTo(EXPECTED_SYMBOL_NAME);
+      }
+    }
+  }
+
+  @Nested
+  class GetFilePath {
+
+    @Nested
+    class ShouldThrowPreconditionViolationException {
+
+      @Test
+      void whenSymbolIsNull() {
+        assertThatExceptionOfType(PreconditionViolationException.class)
+            .isThrownBy(() -> nameProvider.getName(NULL_SYMBOL));
+      }
+    }
+
+    @Nested
+    class ShouldReturnFilePath {
+
+      @Test
+      void whenOnlyFileName() {
+        assertThat(nameProvider.getFilePath(symbol)).isEqualTo(
+            CppMainNameProviderTest.EXPECTED_FILE_PATH);
+      }
+    }
+
+  }
+
+}
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