Methods, contracts and test cases: Mechanism and state changes

≈ 36 min

Methods, contracts and test cases: Mechanism and state changes

A Java method gives one carefully defined job a name. Parameters state the inputs, a return value states the result, and a contract lets another programmer use the method without reading every line inside it.

Learning move. In this lesson, trace what changes, what remains fixed and what evidence a correct process leaves behind.

Worked example. A calculateAverage method receives marks and returns one number. It should not also print a report, change a learner record and open a file: those are separate jobs that can be tested independently.

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Which statement best reflects this lesson's method contract?

One method validates a mark and returns whether it is valid.

Use a vague rule and trust the first result.

Ignore boundary cases and hidden assumptions.

Choose a tool before stating the problem.

Write the key term for this lesson: method contract.

A school system needs a reliable next step. Which choice is most defensible for this topic?

Write static boolean isPass(int mark) and use its returned value.

Store an unexplained guess and call it evidence.

Give every account unrestricted access.

Hide the error so the report looks complete.

A learner can repeat a definition from Methods, contracts and test cases: Mechanism and state changes. Which next task gives stronger evidence of mastery?

Apply the idea to an unfamiliar boundary, error or decision and justify the choice.

Repeat the lesson title without using the concept.

Choose the first option before reading the scenario.

Hide an unexpected result so the answer appears tidy.