Bulk up the test suite for FormulaManager.

Introduces a couple of tests for the FormulaManager test suite in order
to cover all the methods the class exposes. This means it is no longer
necessary to suppress the "unused" warnings.

src/test/java/com/garbagemule/MobArena/formula/FormulaManagerIT.java

@@ -129,6 +129,32 @@ public class FormulaManagerIT {
 
     }
 
+    /**
+     * With custom constants, we are manipulating the internal
+     * state of the manager, so we need to use a local subject.
+     */
+    public static class CustomConstants {
+
+        FormulaManager subject;
+
+        @Before
+        public void setup() {
+            subject = FormulaManager.createDefault();
+        }
+
+        @Test
+        public void resolveRegisteredCustomConstant() {
+            subject.registerConstant("pie", 3.14);
+
+            Formula formula = subject.parse("pie * 2");
+            double result = formula.evaluate(arena);
+
+            double expected = 6.28;
+            assertThat(result, equalTo(expected));
+        }
+
+    }
+
     @RunWith(Parameterized.class)
     public static class DefaultVariables {
 
@@ -262,6 +288,54 @@ public class FormulaManagerIT {
 
     }
 
+    /**
+     * With custom operators, we are manipulating the internal
+     * state of the manager, so we need to use a local subject.
+     */
+    public static class CustomOperators {
+
+        FormulaManager subject;
+
+        @Before
+        public void setup() {
+            subject = FormulaManager.createDefault();
+        }
+
+        @Test
+        public void resolveRegisteredCustomUnaryOperator() {
+            subject.registerUnaryOperator("_", 1, a -> a - 1);
+
+            Formula formula = subject.parse("_(1 + 1)");
+            double result = formula.evaluate(arena);
+
+            double expected = 1;
+            assertThat(result, equalTo(expected));
+        }
+
+        @Test
+        public void resolveRegisteredCustomBinaryOperator1() {
+            subject.registerBinaryOperator("?", 1, true, (a, b) -> (a >= 0) ? a : b);
+
+            Formula formula = subject.parse("5 ? 6");
+            double result = formula.evaluate(arena);
+
+            double expected = 5;
+            assertThat(result, equalTo(expected));
+        }
+
+        @Test
+        public void resolveRegisteredCustomBinaryOperator2() {
+            subject.registerBinaryOperator("?", 1, true, (a, b) -> (a >= 0) ? a : b);
+
+            Formula formula = subject.parse("(5 - 10) ? (3 + 3)");
+            double result = formula.evaluate(arena);
+
+            double expected = 6;
+            assertThat(result, equalTo(expected));
+        }
+
+    }
+
     @RunWith(Parameterized.class)
     public static class DefaultUnaryFunctions {