base64 encoded test fixed

src/test/java/com/example/util/AddFunctionTest.java

@@ -1 +1,30 @@
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+package com.example.util;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+class AddFunctionTest {
+
+    private final AddFunction addFunction = new AddFunction();
+
+    @Test
+    void sumsMultipleValues() {
+        assertEquals(6.0, addFunction.calc(1.0, 2.0, 3.0));
+    }
+
+    @Test
+    void returnsSingleValue() {
+        assertEquals(5.0, addFunction.calc(5.0));
+    }
+
+    @Test
+    void returnsZeroForNoInput() {
+        assertEquals(0.0, addFunction.calc());
+    }
+
+    @Test
+    void sumsNegativeValues() {
+        assertEquals(-3.0, addFunction.calc(-1.0, -2.0));
+    }
+}