Added m04_01_testMortgageCalculatorExists, m04_02_testExistenceOfPriv…

…ateFields

src/test/java/com/h2/Module04_Test.java

@@ -0,0 +1,95 @@
+package com.h2;
+
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Disabled;
+import org.junit.jupiter.api.Test;
+import org.junit.platform.commons.function.Try;
+
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.InputStream;
+import java.io.PrintStream;
+import java.lang.reflect.Field;
+import java.util.*;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+import static org.junit.platform.commons.util.ReflectionUtils.isPrivate;
+import static org.junit.platform.commons.util.ReflectionUtils.tryToLoadClass;
+
+public class Module04_Test {
+    private final String classToFind = "com.h2.MortgageCalculator";
+    private final InputStream systemIn = System.in;
+    private final PrintStream systemOut = System.out;
+
+    private ByteArrayInputStream testIn;
+    private ByteArrayOutputStream testOut;
+
+    @BeforeEach
+    public void setUpOutput() {
+        testOut = new ByteArrayOutputStream();
+        System.setOut(new PrintStream(testOut));
+    }
+
+    private void provideInput(String data) {
+        testIn = new ByteArrayInputStream(data.getBytes());
+        System.setIn(testIn);
+    }
+
+    private String getOutput() {
+        return testOut.toString();
+    }
+
+    @AfterEach
+    public void restoreSystemInputOutput() {
+        System.setIn(systemIn);
+        System.setOut(systemOut);
+    }
+
+    private static Optional<Class<?>> getClass(final String className) {
+        Try<Class<?>> aClass = tryToLoadClass(className);
+        return aClass.toOptional();
+    }
+
+    public Optional<Class<?>> getMortgageClass() {
+        return getClass(classToFind);
+    }
+
+    @Test
+    public void m04_01_testMortgageCalculatorExists() {
+        Optional<Class<?>> maybeClass = getMortgageClass();
+        assertTrue(maybeClass.isPresent(), classToFind + " must be created.");
+    }
+
+    @Test
+    public void m04_02_testExistenceOfPrivateFields() {
+        final Optional<Class<?>> maybeMortgageCalculator = getMortgageClass();
+        assertTrue(maybeMortgageCalculator.isPresent(), classToFind + " must exist");
+        final Class<?> mortgageCalculator = maybeMortgageCalculator.get();
+        final Map<String, Class<?>> expectedFieldsToClass = Map.of(
+                "loanAmount", long.class,
+                "termInYears", int.class,
+                "annualRate", float.class,
+                "monthlyPayment", double.class
+        );
+
+        final Field[] declaredFields = mortgageCalculator.getDeclaredFields();
+        assertEquals(4, declaredFields.length, "4 fields (loanAmount, termInYears, annualRate, monthlyPayment) should be available in " + classToFind);
+
+
+        final Map<String, Class<?>> actualFieldsToClass = new HashMap<>();
+
+        for (final Field field : declaredFields) {
+            assertTrue(expectedFieldsToClass.containsKey(field.getName()), field.getName() + " is not a valid field name. It should be among (loanAmount, termInYears, annualRate, monthlyPayment)");
+            assertTrue(isPrivate(field), field.getName() + " should be declared 'private'");
+            actualFieldsToClass.put(field.getName(), field.getType());
+        }
+
+        expectedFieldsToClass.entrySet()
+                .forEach(e -> {
+                    assertEquals(e.getValue(), actualFieldsToClass.get(e.getKey()), e.getKey() + " must be of type " + e.getValue());
+                });
+
+    }
+}