42 lines
1.5 KiB
Markdown
42 lines
1.5 KiB
Markdown
# On assertions
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Answer the following questions:
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1. The following assertion fails `assertTrue(3 * .4 == 1.2)`. Explain why and describe how this type of check should be done.
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2. What is the difference between `assertEquals` and `assertSame`? Show scenarios where they produce the same result and scenarios where they do not produce the same result.
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3. In classes we saw that `fail` is useful to mark code that should not be executed because an exception was expected before. Find other uses for `fail`. Explain the use case and add an example.
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4. In JUnit 4, an exception was expected using the `@Test` annotation, while in JUnit 5 there is a special assertion method `assertThrows`. In your opinion, what are the advantages of this new way of checking expected exceptions?
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## Answer
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1.
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Les flottants sont codés en binaire avec des divisions de 2, certaines valeurs sont donc impossibles à avoir exactement en flottant, comme 1.2 et 0.4
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2.
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assertEquals vérifie si les valeurs des objets sont identiques alors que assertSame vérifie si l'objet est identique.
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Par exemple
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```java
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String s = "test";
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assertSame(s,s);
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assertEquals(s,s);
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```
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revoient true
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alors que
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```java
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String s = "te";
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String s2 = "test";
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s += "st"; //sinon l'optimisation du compilateur Java met le même objet sur s et s2
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assertSame("test",str+"st");
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assertEquals("test",str+"st");
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```
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assertSame renvoit false, alors que assertEquals renvoit true
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3.
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4.
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Cela permet de rendre les test plus uniforme, dans junit 5 on comprend mieux où exactement on attend l'exception.
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