1_assertions.md

Step #1: Introducing Assertions

1.1: Create the Assertions class & assertTrue

1. Create a mcunit package
2. Create a class Assertions
3. Define a static method assertTrue throwing an AssertionError

package mcunit;

public class Assertions {

    public static void assertTrue(boolean condition) {
        if (!condition)
            throw new AssertionError();
    }

}

4. Update Main to check assertions usage

public static void main(String[] args) {
    System.out.println("# 2AA4 - McUnit Demo");

    int x = 1;
    int y = 1;

    try {
        System.out.println("## Case 1: x + y == 2 (should PASS)");
        assertTrue(x + y == 2);
        System.out.println("PASSED");
    } catch(AssertionError ae) {
        System.out.println("FAILED");
    }

    try {
        System.out.println("## Case 2: x + y == 4 (should FAIL)");
        assertTrue(x + y == 4);
        System.out.println("PASSED");
    } catch(AssertionError ae) {
        System.out.println("FAILED");
    }

}

5. Compile and execute

mosser@azrael 2aa4-mcunit % mvn -q clean package
mosser@azrael 2aa4-mcunit % mvn -q exec:java
# 2AA4 - McUnit Demo
## Case 1: x + y == 2 (should PASS)
PASSED
## Case 2: x + y == 4 (should FAIL)
FAILED

6. Record into VCS

mosser@azrael 2aa4-mcunit % git add src/main/java/Main.java src/main/java/mcunit/Assertions.java 
mosser@azrael 2aa4-mcunit % git commit -m "supporting assertTrue"

1.2: Introduce assertFalse

1. Define an assertFalse method in Assertions

public static void assertFalse(boolean condition) {
    assertTrue(!condition);
}

2. Update Main to make the second test case pass by using assertFalse

try {
    System.out.println("## Case 2: x + y != 4 (should PASS)");
    assertFalse(x + y == 4);
    System.out.println("PASSED");
} catch(AssertionError ae) {
    System.out.println("FAILED");
}

3. Compile and execute

mosser@azrael 2aa4-mcunit % mvn -q clean package
mosser@azrael 2aa4-mcunit % mvn -q exec:java    
# 2AA4 - McUnit Demo
## Case 1: x + y == 2 (should PASS)
PASSED
## Case 2: x + y != 4 (should PASS)
PASSED

4. Record into VCS

mosser@azrael 2aa4-mcunit % git add src/main/java/Main.java src/main/java/mcunit/Assertions.java 
mosser@azrael 2aa4-mcunit % git commit -m "supporting assertFalse"

1.3 Introduce assertEquals & assertNotEquals

1. Define an assertEquals method in Assertions.
   • It leverages the public contract defined by Object::equals (reflexive, transitive, symmetric)
   • Technical debt: left can't be null.

public static void assertEquals(Object left, Object right) {
    assertTrue(left.equals(right));
}

public static void assertNotEquals(Object left, Object right) {
    assertFalse(left.equals(right));
}

2. Update Main to get rid of the low-level assertions and used business-driven ones

try {
   System.out.println("## Case 1: x + y == 2 (should PASS)");
   assertEquals(x + y, 2);
   System.out.println("PASSED");
} catch(AssertionError ae) {
   System.out.println("FAILED");
}

try {
   System.out.println("## Case 2: x + y != 4 (should PASS)");
   assertNotEquals(x + y, 4);
   System.out.println("PASSED");
} catch(AssertionError ae) {
   System.out.println("FAILED");
}

3. Compile and execute

mosser@azrael 2aa4-mcunit % mvn -q clean package                                                 
mosser@azrael 2aa4-mcunit % mvn -q exec:java                                                     
# 2AA4 - McUnit Demo
## Case 1: x + y == 2 (should PASS)
PASSED
## Case 2: x + y != 4 (should PASS)
PASSED

4. Record into the VCS

mosser@azrael 2aa4-mcunit % git add src/main/java/Main.java src/main/java/mcunit/Assertions.java 
mosser@azrael 2aa4-mcunit % git commit -m "supporting assertEquals and assertNotEquals"

1.4 Release and publish

mosser@azrael 2aa4-mcunit % git tag step_1
mosser@azrael 2aa4-mcunit % git push --tags
mosser@azrael 2aa4-mcunit % git push