added logic to ConVolume and Unittest for the function and fixed wrong test results

src/main/c/ConvertMode.c

@@ -176,6 +176,18 @@ double getValue(int choice) {
 
             printf("\nThe convertet result is %dlf %d²", result, Distance[endingUnit]);
             break;
+
+        case 12://char Distance[] = { 'mm', 'cm', 'm', 'km', 'feet/inch', 'miles'};
+            printf("\nEnter what the Unit is starting with (0 mm, 1 cm, 2 m , 3 km,): ");
+            scanf("%d", &startingUnit);
+
+            printf("\nEnter what the value should it be changed to (0 mm, 1 cm, 2 m , 3 km,): ");
+            scanf("%d", &endingUnit);
+
+            result = ConArea(value, startingUnit, endingUnit);
+
+            printf("\nThe convertet result is %dlf %d³", result, Distance[endingUnit]);
+            break;
         }
     }
 }
@@ -220,9 +232,7 @@ double ConSpeed(double speed, int startingUnit, int endingUnit) {
 */
 
 
-double ConVolume() {
 
-}
 
 double ConTime() {
 

src/main/c/main_taschenrechner.c

@@ -849,6 +849,106 @@ double ConData(double data, int startingUnit, int endingUnit) {
     }
 }
 
+double ConVolume(double volum, int startingUnit, int endingUnit) {
+    switch (startingUnit)
+    {
+    case 0: //mm to x
+        switch (endingUnit)
+        {
+        case 0: //1mm
+            return volum;
+            break;
+
+        case 1: //0.001cm
+            return volum / 1000;
+            break;
+
+        case 2: //0.000000001m
+            return volum / 1000000000;
+            break;
+
+        case 3: //0.000000000000001km
+            return volum / 1000000000000000000;
+            break;
+
+        default:
+            break;
+        }
+
+    case 1: //cm to x
+        switch (endingUnit)
+        {
+        case 0: //1000
+            return volum * 1000;
+            break;
+
+        case 1: //1
+            return volum;
+            break;
+
+        case 2: //0.000001
+            return volum / 1000000;
+            break;
+
+        case 3: //0.0000000000001
+            return volum / 1000000000000000;
+            break;
+
+        default:
+            break;
+        }
+
+    case 2: //m to x
+        switch (endingUnit)
+        {
+        case 0: //100000000
+            return volum * 1000000000;
+            break;
+
+        case 1: //1000000
+            return volum * 1000000;
+            break;
+
+        case 2: //1
+            return volum;
+            break;
+
+        case 3: //0.000000001
+            return volum / 1000000000;
+            break;
+
+        default:
+            break;
+        }
+
+    case 3:// km to x
+        switch (endingUnit)
+        {
+        case 0: // 1000000000000000000
+            return volum * 1000000000000000000;
+            break;
+
+        case 1: // 1000000000000000
+            return volum * 1000000000000000;
+            break;
+
+        case 2: // 1000000000 m
+            return volum * 1000000000;
+            break;
+
+        case 3: //1 km
+            return volum;
+            break;
+
+        default:
+            break;
+        }
+
+    default:
+        break;
+    }
+}
+
 
 //..
 // graphMode

src/main/c/taschenrechner.h

@@ -79,4 +79,6 @@ double ConData(double data, int startingUnit, int endingUnit);
 
 double ConArea(double area, int startingUnit, int endingUnit);
 
+double ConVolume(double volum, int startingUnit, int endingUnit);
+
 #endif // TASCHENRECHNER_H

src/test/c/test_taschenrechner.c

@@ -90,8 +90,15 @@ void test_ConData(void) {//5 b to kb
 
 void test_ConArea(void) {//5 mm to cm
     double result = ConData(5, 0, 1);
-    TEST_ASSERT_EQUAL(0.0005), result);
+    TEST_ASSERT_EQUAL(0.05), result);
 }
 
+void test_ConVolume(void) {//5 mm to cm
+    double result = ConData(5, 0, 1);
+    TEST_ASSERT_EQUAL(0.005), result);
+}
+
+
+
 
 #endif // TEST