How to conditionally skip a Mocha test in TypeScript

Question

While this SO article covers how to skip tests in javascript. The discussion doesn't cover how to do the same thing in TypeScript.

Example of not working code:

describe('Example test suite',() => {  
                                                     
  before(async () => {                               
    if(true) {                                       
      console.log('Unexpected condition. Test results may be invalid. Skipping tests.');  
      this.skip();                                                                                      
    }                                                                                                      
  });                                                                                                      
                                                                                                           
  it('it will do something',async () => {                                                                  
    console.log('This should not run.');                                                                   
  });                                                                                                      
                           
});

Results:

error TS2532: Object is possibly 'undefined'.

score 1 · Accepted Answer · answered Jul 13 '22 at 17:38

I used the CocNvim plugin for neovim to do some inline introspection into the mocha type definitions and found the following solution works:

describe('Example test suite',function(this:Mocha.Suite) {  
  const suite = this;                                  
                                                     
  before(async () => {                               
    if(true) {                                       
      console.log('Unexpected condition. Test results may be invalid. Skipping tests.');      
      suite.ctx.skip();                              
    }                                                
  });                                                
                                                     
  it('it will do something',async () => {            
    console.log('This will not run.');               
  });                                                  
});

Note the intentional use of function() instead of an arrow function in the describe handler. This is because arrow functions cannot define their this:type.

How to conditionally skip a Mocha test in TypeScript

1 Answers1

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