Test steps for organized output in Deno - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of organizing test steps in Deno testing?

Organizing test steps helps keep tests clear and easy to follow. It makes debugging simpler and ensures tests run in a logical order.

beginner

How do you group related test steps in Deno?

You use the Deno.test function with nested steps inside it. Each step can be defined with t.step() to organize smaller parts of a test.

intermediate

What is the benefit of using t.step() inside a Deno test?

It breaks a test into smaller, named parts. This helps show detailed output for each step and makes it easier to find where a test failed.

intermediate

How can you make test output more readable in Deno?

By naming each test and step clearly and using nested steps, the output shows a clear hierarchy. This helps understand what each part tests and its result.

beginner

Show a simple example of organized test steps in Deno.

```ts Deno.test("Main test", async (t) => { await t.step("Step 1: Setup", () => { // setup code }); await t.step("Step 2: Action", () => { // action code }); await t.step("Step 3: Assert", () => { // assertions }); }); ```

Which Deno function is used to define a test?

A test.run

B runTest

C Deno.test

D testStep

Deno uses the Deno.test function to define tests.

How do you create a nested test step inside a Deno test?

A Using <code>t.step()</code>

B Using <code>Deno.step()</code>

C Using <code>test.step()</code>

D Using <code>stepTest()</code>

Inside a test callback, t.step() creates nested steps.

Why organize test steps in Deno?

A To improve output clarity and debugging

B To make tests run faster

C To reduce code size

D To avoid writing assertions

Organizing steps improves clarity and helps find errors easily.

What does each t.step() require as arguments?

A Only a name string

B A name and a callback function

C Only a callback function

D No arguments

t.step() needs a descriptive name and a function to run.

What will happen if a nested step fails in Deno?

A All tests pass anyway

B The whole test suite stops immediately

C The failure is ignored

D Only that step fails, and output shows the failure clearly

Deno shows which step failed, helping you fix that part.

Explain how to organize test steps in Deno for clear output.

Think about breaking tests into smaller parts with names.

Describe the advantages of using nested test steps in Deno.

Focus on output clarity and error tracking.

Practice

1. What is the main benefit of organizing test steps clearly in deno.test?

easy

A. Automatically fixes code errors

B. Runs tests faster

C. Reduces the number of tests needed

D. Makes tests easier to read and debug

Solution

1. Step 1: Understand the purpose of test organization

   Organizing test steps clearly helps anyone reading the test understand what each part does.

2. Step 2: Connect organization to debugging ease

   Clear steps make it easier to find where a test fails and fix it quickly.

3. Final Answer:

   Makes tests easier to read and debug -> Option D

4. Quick Check:

   Clear test steps = easier debugging [OK]

Hint: Clear test steps help find bugs faster [OK]

Common Mistakes:

• Thinking organization speeds up test execution
• Believing fewer tests are needed with organization
• Assuming tests fix code automatically

2. Which of the following is the correct way to define a test with a clear name in Deno?

easy

A. deno.check('Check addition', () => { /* test code */ })

B. test('Check addition', () => { /* test code */ })

C. deno.test('Check addition', () => { /* test code */ })

D. deno.runTest('Check addition', () => { /* test code */ })

Solution

1. Step 1: Recall Deno test syntax

   Deno uses the deno.test function to define tests with a name and a function.

2. Step 2: Identify the correct function call

   Only deno.test matches the correct syntax; others are invalid or do not exist.

3. Final Answer:

   deno.test('Check addition', () => { /* test code */ }) -> Option C

4. Quick Check:

   Use deno.test() to define tests [OK]

Hint: Use deno.test() with a descriptive name [OK]

Common Mistakes:

• Using just test() without deno prefix
• Using non-existent functions like deno.check()
• Confusing runTest with test

3. Consider this Deno test code:

deno.test('Sum test', () => {
  const a = 2;
  const b = 3;
  const result = a + b;
  if (result !== 5) throw new Error('Sum failed');
});

What happens when you run this test?

medium

A. Test outputs the sum value

B. Test passes silently with no errors

C. Syntax error stops the test

D. Test fails with 'Sum failed' error

Solution

1. Step 1: Analyze the sum calculation

   Variables a=2 and b=3 sum to 5, so result is 5.

2. Step 2: Check the condition for error

   The condition result !== 5 is false, so no error is thrown.

3. Final Answer:

   Test passes silently with no errors -> Option B

4. Quick Check:

   Correct sum means no error thrown [OK]

Hint: Check if error condition matches actual result [OK]

Common Mistakes:

• Assuming test outputs values automatically
• Thinking test fails without error throw
• Confusing syntax error with runtime error

4. This Deno test code has an error:

deno.test('Check value', () => {
  const val = 10
  if val !== 10 {
    throw new Error('Value mismatch')
  }
});

What is the error and how to fix it?

medium

A. Missing parentheses in if condition; add parentheses

B. Missing semicolon after val declaration; add semicolon

C. Wrong function name; use deno.check instead of deno.test

D. Cannot throw error inside test; remove throw statement

Solution

1. Step 1: Identify syntax error in if statement

   The if condition lacks parentheses around val !== 10, which is required in JavaScript/TypeScript.

2. Step 2: Fix the if statement syntax

   Add parentheses: if (val !== 10) { ... } to correct the syntax.

3. Final Answer:

   Missing parentheses in if condition; add parentheses -> Option A

4. Quick Check:

   If conditions need parentheses [OK]

Hint: Always wrap if conditions in parentheses [OK]

Common Mistakes:

• Ignoring missing parentheses error
• Thinking semicolons cause this error
• Confusing function names in Deno tests

5. You want to organize a Deno test that checks multiple steps: fetching data, validating it, and saving results. Which approach best organizes these steps for clear output?

hard

A. Use one test with clear comments and separate code blocks for each step

B. Write all steps in one line without comments

C. Create multiple tests but with vague names like 'Test 1', 'Test 2'

D. Skip comments and rely on console.log for clarity

Solution

1. Step 1: Understand importance of clear test structure

   Organizing steps with comments and separate code blocks helps readers follow the test flow easily.

2. Step 2: Compare options for clarity

   One test with clear comments is better than vague test names or no comments, which confuse readers.

3. Final Answer:

   Use one test with clear comments and separate code blocks for each step -> Option A

4. Quick Check:

   Clear comments + code blocks = organized tests [OK]

Hint: Comment each step clearly inside one test [OK]

Common Mistakes:

• Writing unclear test names
• Skipping comments thinking code is self-explanatory
• Relying only on console logs for understanding