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Testing MDX Parser Implementation in GatsbyJS

This test suite validates the MDX parsing functionality in Gatsby Recipes, focusing on step partitioning and error handling for JSX content. The tests ensure proper extraction of MDX components and validation of JSX syntax.

Test Coverage Overview

The test suite provides comprehensive coverage of MDX parsing capabilities.

Key areas tested include:

Step partitioning of MDX content
Validation of component extraction
Error handling for malformed JSX
Integration with file system operations

Implementation Analysis

The testing approach utilizes Jest’s async/await pattern for handling file operations and parsing tasks. The implementation leverages fixture-based testing with pre-defined MDX content, ensuring consistent test scenarios across different environments.

Technical patterns include:

Asynchronous test execution
File system fixture loading
Error boundary testing
Component structure validation

Technical Details

Testing tools and setup:

Jest as the primary testing framework
fs-extra for file system operations
Custom parser implementation
MDX fixture files
Path resolution utilities

Best Practices Demonstrated

The test suite exemplifies several testing best practices for parser validation. It demonstrates proper separation of concerns, robust error handling, and comprehensive component validation.

Notable practices include:

Isolated test cases
Fixture-based testing
Explicit error checking
Clear test case organization

gatsbyjs/gatsby

deprecated-packages/gatsby-recipes/src/parser/index.test.js

            
const fs = require(`fs-extra`)
const path = require(`path`)

const parser = require(`.`)

const fixturePath = path.join(__dirname, `fixtures/prettier-git-hook.mdx`)
const fixtureSrc = fs.readFileSync(fixturePath, `utf8`)

test(`partitions the MDX into steps`, async () => {
  const result = await parser.parse(fixtureSrc)

  expect(result.stepsAsMdx[0]).toMatch(
    `# Automatically run Prettier on Git commits`
  )
  expect(result.stepsAsMdx[1]).toMatch(`<NPMPackage`)
  expect(result.stepsAsMdx[2]).toMatch(`<NPMPackageJson`)
  expect(result.stepsAsMdx[3]).toMatch(`<File`)
})

test(`raises an error if JSX doesn't parse`, async () => {
  try {
    await parser.parse(`# Hello, world!
---
<NPMScript name="foo" command="bar" /
`)
  } catch (e) {
    expect(e).toBeTruthy()
  }
})