deno test for testing - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the testing module in Deno.

Deno

import { [1] } from "https://deno.land/std/testing/asserts.ts";

Drag options to blanks, or click blank then click option'

AassertEquals

Btest

Cassert

DrunTests

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'test' instead of 'assertEquals' for assertions.

Trying to import from a wrong URL.

The assertEquals function is imported from Deno's standard testing asserts module to compare expected and actual values in tests.

2fill in blank

medium

Complete the code to define a test case using Deno's test function.

Deno

Deno.[1]("example test", () => {
  // test code here
});

Drag options to blanks, or click blank then click option'

Aassert

Brun

Ctest

Dcheck

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'run' or 'check' which are not Deno test functions.

Trying to call 'assert' as a test function.

Deno uses the test function to define test cases with a name and a function containing the test code.

3fill in blank

hard

Fix the error in the test assertion to correctly compare values.

Deno

Deno.test("sum test", () => {
  const result = 2 + 3;
  assert[1](result, 5);
});

Drag options to blanks, or click blank then click option'

AEqual

BStrictEqual

CDeepEqual

DEquals

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'assertEqual' which does not exist in Deno.

Using 'assertStrictEqual' which is not part of Deno's standard asserts.

The correct assertion function is assertEquals which compares two values for equality in Deno tests.

4fill in blank

hard

Fill both blanks to create a test that checks if a string includes a substring.

Deno

Deno.test("string includes test", () => {
  const text = "hello world";
  [1](text.[2]("world"));
});

Drag options to blanks, or click blank then click option'

Aassert

Bincludes

CindexOf

DassertEquals

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'assertEquals' instead of 'assert' for boolean checks.

Using 'indexOf' without comparing to -1.

Use assert to check a boolean condition and includes to test if the string contains the substring.

5fill in blank

hard

Fill all three blanks to write a test that verifies an async function returns the expected value.

Deno

Deno.test("async fetch test", async () => {
  const data = await fetchData();
  assert[1](data.[2], [3]);
});

Drag options to blanks, or click blank then click option'

AEquals

Bvalue

C"success"

Dassert

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'assert' instead of 'assertEquals' for value comparison.

Forgetting to await the async function.

Use assertEquals to compare the value property of data to the expected string "success".

Practice

1. What is the main purpose of using deno test in your code?

easy

A. To check if your code works as expected by running tests

B. To deploy your code to a server

C. To format your code automatically

D. To create a new Deno project

Solution

1. Step 1: Understand the role of deno test

   deno test is a command used to run tests written in your code to verify correctness.

2. Step 2: Compare with other options

   Deploying, formatting, or creating projects are not related to testing functionality.

3. Final Answer:

   To check if your code works as expected by running tests -> Option A

4. Quick Check:

   Testing = Check code correctness [OK]

Hint: Remember: testing means checking code correctness [OK]

Common Mistakes:

• Confusing testing with deployment
• Thinking deno test formats code
• Assuming it creates projects

2. Which of the following is the correct way to write a simple test in Deno?

easy

A. deno.test(() => { assertEquals(1 + 1, 2); });

B. test deno { assertEquals(1 + 1, 2); }

C. deno.test = () => { assertEquals(1 + 1, 2); }

D. test(() => assertEquals(1 + 1, 2));

Solution

1. Step 1: Identify correct test syntax in Deno

   The correct syntax uses deno.test as a function with a callback containing assertions.

2. Step 2: Check each option

   deno.test(() => { assertEquals(1 + 1, 2); }); correctly uses deno.test(() => { ... }). Options A, B, and D have syntax errors or incorrect usage.

3. Final Answer:

   deno.test(() => { assertEquals(1 + 1, 2); }); -> Option A

4. Quick Check:

   Correct test syntax = deno.test(() => { assertEquals(1 + 1, 2); }); [OK]

Hint: Use deno.test with a function callback [OK]

Common Mistakes:

• Using incorrect keywords like 'test deno'
• Assigning instead of calling deno.test
• Omitting 'deno.' prefix

3. What will be the output when running this test code with deno test?

import { assertEquals } from "https://deno.land/std@0.177.0/testing/asserts.ts";
deno.test("sum test", () => {
  assertEquals(2 + 2, 4);
});

medium

A. Syntax error due to import statement

B. Test fails with assertion error

C. Test passes with no errors

D. Runtime error: deno.test is not a function

Solution

1. Step 1: Analyze the test code logic

   The test checks if 2 + 2 equals 4 using assertEquals, which is true.

2. Step 2: Consider syntax and runtime

   The import statement is correct, and deno.test is valid in Deno environment.

3. Final Answer:

   Test passes with no errors -> Option C

4. Quick Check:

   Correct assertion = Test passes [OK]

Hint: True assertions mean passing tests [OK]

Common Mistakes:

• Thinking import causes syntax error
• Confusing assertion failure with success
• Assuming deno.test is undefined

4. Identify the error in this test code snippet:

import { assertEquals } from "https://deno.land/std/testing/asserts.ts";
deno.test("check", () => {
  assertEquals(5, 2 + 2);
});

medium

A. assertEquals is not imported correctly

B. The assertion will fail because 5 is not equal to 4

C. deno.test is used incorrectly without a name

D. The import URL is missing the version number

Solution

1. Step 1: Check the import statement

   The import URL lacks a version number, which is required for stable imports in Deno.

2. Step 2: Verify other parts

   The assertion will fail logically, but the question asks for the error in the snippet, and missing version is a syntax/runtime error.

3. Final Answer:

   The import URL is missing the version number -> Option D

4. Quick Check:

   Stable imports need version numbers [OK]

Hint: Always include version in import URLs [OK]

Common Mistakes:

• Ignoring missing version in import URL
• Confusing assertion failure with syntax error
• Assuming deno.test needs no name

5. You want to write multiple tests in one file using deno test. Which approach correctly groups tests with descriptive names and runs them all?

hard

A. Write one deno.test with multiple assertions but no names

B. Use multiple deno.test calls each with a unique name and callback function

C. Call deno.test inside a loop without names

D. Use deno.runTests() to run tests automatically

Solution

1. Step 1: Understand how to organize multiple tests

   Each test should have a unique name and a callback function using deno.test.

2. Step 2: Evaluate options

   Use multiple deno.test calls each with a unique name and callback function correctly uses multiple named tests. Write one deno.test with multiple assertions but no names lacks test names, making results unclear. Call deno.test inside a loop without names uses a loop without names, which is not recommended. Use deno.runTests() to run tests automatically is invalid; deno.runTests() does not exist.

3. Final Answer:

   Use multiple deno.test calls each with a unique name and callback function -> Option B

4. Quick Check:

   Multiple named tests = Use multiple deno.test calls each with a unique name and callback function [OK]

Hint: Name each test separately with deno.test [OK]

Common Mistakes:

• Writing unnamed tests
• Using loops without test names
• Assuming deno.runTests() exists