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Testing Text Truncation Utilities in GatsbyJS

This test suite validates the text truncation utility functions in the Gatsby preload fonts plugin. It specifically focuses on the ellipses function behavior, ensuring proper text handling and truncation with ellipsis.

Test Coverage Overview

The test suite provides comprehensive coverage of the ellipses utility function.

Key areas tested include:

Text handling below maximum length
Edge case handling at exact maximum length
Proper truncation with ellipsis for text exceeding limits

Implementation Analysis

The testing approach uses Jest’s describe/it pattern for clear test organization. The implementation follows BDD-style testing with explicit test cases for different text length scenarios.

Technical patterns include:

Nested describe blocks for logical grouping
Direct function import testing
Expect assertions with exact matching

Technical Details

Testing infrastructure includes:

Jest as the primary testing framework
Direct module imports for utility functions
String manipulation testing
Boundary value testing methodology

Best Practices Demonstrated

The test suite exemplifies several testing best practices for utility functions.

Notable practices include:

Clear test case separation
Descriptive test naming
Boundary value testing
Single responsibility principle in test cases
Consistent assertion patterns

gatsbyjs/gatsby

packages/gatsby-plugin-preload-fonts/src/__tests__/utils.test.js

            
const { ellipses } = require(`../prepare/utils`)

describe(`utils`, () => {
  describe(`ellipses`, () => {
    it(`does nothing to text under max length`, () => {
      expect(ellipses(`some text`, 10)).toBe(`some text`)
    })

    it(`does nothing to text at max length`, () => {
      expect(ellipses(`some text`, 9)).toBe(`some text`)
    })

    it(`truncates text over max length with \`...\``, () => {
      expect(ellipses(`some text`, 4)).toBe(`some...`)
    })
  })
})