record/coverage [20260422-192751]

src/main/java/com/phalanx/calc/MathOps.java

@@ -29,4 +29,22 @@ public static double divide(double a, double b) {
         }
         return a / b;
     }
+
+    public static double percentage(double part, double whole) {
+        if (whole == 0) {
+            throw new ArithmeticException("cannot compute percentage of zero");
+        }
+        return (part / whole) * 100;
+    }
+
+    public static double average(double[] values) {
+        if (values.length == 0) {
+            throw new IllegalArgumentException("cannot average an empty list");
+        }
+        double sum = 0;
+        for (double v : values) {
+            sum += v;
+        }
+        return sum / values.length;
+    }
 }

src/test/java/com/phalanx/calc/MathOpsTest.java

@@ -61,4 +61,48 @@ void divideFractions() {
     void divideByZeroThrows() {
         assertThrows(ArithmeticException.class, () -> MathOps.divide(1, 0));
     }
+
+    // --- percentage ---
+
+    @Test
+    void percentageHalf() {
+        assertEquals(50.0, MathOps.percentage(1, 2));
+    }
+
+    @Test
+    void percentageHundred() {
+        assertEquals(100.0, MathOps.percentage(5, 5));
+    }
+
+    @Test
+    void percentageSmall() {
+        assertEquals(25.0, MathOps.percentage(1, 4));
+    }
+
+    @Test
+    void percentageOfZeroThrows() {
+        assertThrows(ArithmeticException.class, () -> MathOps.percentage(5, 0));
+    }
+
+    // --- average ---
+
+    @Test
+    void averageSingleValue() {
+        assertEquals(7.0, MathOps.average(new double[]{7}));
+    }
+
+    @Test
+    void averageMultipleValues() {
+        assertEquals(3.0, MathOps.average(new double[]{1, 2, 3, 4, 5}));
+    }
+
+    @Test
+    void averageWithNegatives() {
+        assertEquals(0.0, MathOps.average(new double[]{-1, 0, 1}));
+    }
+
+    @Test
+    void averageEmptyThrows() {
+        assertThrows(IllegalArgumentException.class, () -> MathOps.average(new double[]{}));
+    }
 }