Test steps for organized output in Deno - Step-by-Step Execution

Concept Flow - Test steps for organized output

Define Test Steps

↓

Run Each Step Sequentially

↓

Capture Step Output

↓

Organize Outputs

↓

Display or Assert Results

↓

End

This flow shows how test steps are defined, run one by one, their outputs collected and organized, then results are shown or checked.

Execution Sample

Deno

import { assertEquals } from "https://deno.land/std/testing/asserts.ts";

Deno.test("Organized test steps", () => {
  const steps = [];
  steps.push(() => "Step 1 done");
  steps.push(() => "Step 2 done");

  const results = steps.map(step => step());
  assertEquals(results, ["Step 1 done", "Step 2 done"]);
});

This test runs two simple steps, collects their outputs in order, and checks the outputs match expected results.

Execution Table

Step	Action	Output	Results Array State
1	Define step function returning 'Step 1 done'	N/A	[]
2	Define step function returning 'Step 2 done'	N/A	[]
3	Run step 1 function	Step 1 done	["Step 1 done"]
4	Run step 2 function	Step 2 done	["Step 1 done", "Step 2 done"]
5	Assert results array equals expected	Pass	["Step 1 done", "Step 2 done"]

💡 All steps executed and outputs collected; assertion passed confirming organized output.

Variable Tracker

Variable	Start	After Step 1	After Step 2	Final
steps	[]	[step1]	[step1, step2]	[step1, step2]
results	[]	["Step 1 done"]	["Step 1 done", "Step 2 done"]	["Step 1 done", "Step 2 done"]

Key Moments - 2 Insights

Why do we collect outputs in an array instead of printing immediately?

Collecting outputs in an array (see execution_table rows 3 and 4) lets us organize and check all results together, making tests clearer and easier to verify.

What happens if one step fails or returns unexpected output?

The assertion in row 5 will fail, showing the test did not pass, so you know which step's output was wrong or missing.

Visual Quiz - 3 Questions

Look at the execution_table, what is the results array after step 2 runs?

A ["Step 1 done", "Step 2 done"]

B ["Step 2 done"]

C []

D ["Step 1 done"]

💡 Hint

Check the 'Results Array State' column at step 4 in the execution_table.

At which step does the test confirm all outputs are correct?

A Step 3

B Step 1

C Step 5

D Step 4

💡 Hint

Look for the step where assertion happens in the execution_table.

If the first step returned 'Failed' instead of 'Step 1 done', what would happen?

A The results array would still match expected and test passes

B The results array would contain 'Failed' and test would fail at assertion

C The test would skip the second step

D The test would crash immediately

💡 Hint

Refer to variable_tracker and execution_table rows 3-5 about outputs and assertion.

Concept Snapshot

Test Steps for Organized Output in Deno:
- Define each test step as a function
- Run steps sequentially
- Collect outputs in an array
- Assert collected outputs match expected
- Helps keep tests clear and results easy to check

Full Transcript

This example shows how to organize test steps in Deno by defining functions for each step, running them one after another, collecting their outputs in an array, and then checking that array matches expected results. This method helps keep tests neat and easy to understand. The execution table traces each step's action and how the results array grows. The variable tracker shows how the steps and results variables change. Key moments clarify why collecting outputs is useful and what happens if outputs differ. The quiz questions check understanding of the results array state and assertion step.

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