Increase code quality by increasing code coverage: lib/parse-args.js

refactor: removing / testing lines of code for lib/parse-args.js to increase coverage. (#447)
test: Adding a test case for NODE_V8_COVERAGE and changing the describe block title. (#447)
test: Early exit branch test for hideInstrumenteeArgs function. (#447)
test: Adding test for relative paths for relative report directory cli option. (#447)
test: Adding test case for relative paths for temporary directory cli option. (#447)
test: Adding test for passing node.js arguments to c8. (#447)

lib/parse-args.js

@@ -30,7 +30,8 @@ function buildYargs (withCommands = false) {
       alias: ['o', 'report-dir'],
       group: 'Reporting options',
       describe: 'directory where coverage reports will be output to',
-      default: './coverage'
+      default: './coverage',
+      type: 'string'
     })
     .options('all', {
       default: false,
@@ -126,7 +127,8 @@ function buildYargs (withCommands = false) {
     })
     .option('temp-directory', {
       describe: 'directory V8 coverage data is written to and read from',
-      default: process.env.NODE_V8_COVERAGE
+      default: process.env.NODE_V8_COVERAGE,
+      type: 'string'
     })
     .option('clean', {
       default: true,
@@ -207,12 +209,12 @@ function hideInstrumenteeArgs () {
   let argv = process.argv.slice(2)
   const yargv = parser(argv)
 
-  if (!yargv._.length) return argv
-
-  // drop all the arguments after the bin being
-  // instrumented by c8.
-  argv = argv.slice(0, argv.indexOf(yargv._[0]))
-  argv.push(yargv._[0])
+  if (yargv._.length !== 0) {
+    // drop all the arguments after the bin being
+    // instrumented by c8.
+    argv = argv.slice(0, argv.indexOf(yargv._[0]))
+    argv.push(yargv._[0])
+  }
 
   return argv
 }

test/integration.js.snap

@@ -166,7 +166,7 @@ All files                              |    3.52 |     12.5 |    6.52 |    3.52
   prettify.js                          |       0 |        0 |       0 |       0 | 1-2                    
   sorter.js                            |       0 |        0 |       0 |       0 | 1-196                  
  c8/lib                                |       0 |        0 |       0 |       0 |                        
-  parse-args.js                        |       0 |        0 |       0 |       0 | 1-224                  
+  parse-args.js                        |       0 |        0 |       0 |       0 | 1-226                  
   report.js                            |       0 |        0 |       0 |       0 | 1-402                  
   source-map-from-file.js              |       0 |        0 |       0 |       0 | 1-100                  
  c8/lib/commands                       |       0 |        0 |       0 |       0 |                        
@@ -531,7 +531,7 @@ All files                              |    3.52 |     12.5 |    6.52 |    3.52
   prettify.js                          |       0 |        0 |       0 |       0 | 1-2                    
   sorter.js                            |       0 |        0 |       0 |       0 | 1-196                  
  c8/lib                                |       0 |        0 |       0 |       0 |                        
-  parse-args.js                        |       0 |        0 |       0 |       0 | 1-224                  
+  parse-args.js                        |       0 |        0 |       0 |       0 | 1-226                  
   report.js                            |       0 |        0 |       0 |       0 | 1-402                  
   source-map-from-file.js              |       0 |        0 |       0 |       0 | 1-100                  
  c8/lib/commands                       |       0 |        0 |       0 |       0 |                        

test/parse-args.js

@@ -15,6 +15,11 @@ describe('parse-args', () => {
       const instrumenterArgs = hideInstrumenteeArgs()
       instrumenterArgs.should.eql(['--foo=99', 'my-app'])
     })
+    it('test early exit from function if no arguments are passed', () => {
+      process.argv = []
+      const instrumenterArgs = hideInstrumenteeArgs()
+      instrumenterArgs.length.should.eql(0)
+    })
   })
 
   describe('hideInstrumenterArgs', () => {
@@ -25,6 +30,13 @@ describe('parse-args', () => {
       instrumenteeArgs.should.eql(['my-app', '--help'])
       argv.tempDirectory.endsWith(join('coverage', 'tmp')).should.be.equal(true)
     })
+    it('interprets first args after -- as Node.js execArgv', () => {
+      const expected = [process.execPath, '--expose-gc', 'index.js']
+      process.argv = ['node', 'c8', '--', '--expose-gc', 'index.js']
+      const argv = buildYargs().parse(hideInstrumenteeArgs())
+      const munged = hideInstrumenterArgs(argv)
+      munged.should.deep.equal(expected)
+    })
   })
 
   describe('with NODE_V8_COVERAGE already set', () => {
@@ -34,8 +46,20 @@ describe('parse-args', () => {
       process.argv = ['node', 'c8', '--foo=99', 'my-app', '--help']
       const argv = buildYargs().parse(hideInstrumenteeArgs())
       argv.tempDirectory.endsWith('/coverage/tmp_').should.be.equal(true)
+      delete process.env.NODE_V8_COVERAGE
+      process.env.NODE_V8_COVERAGE = NODE_V8_COVERAGE
+    })
+    /** Commenting out till the print config PR is ready * /
+    it('should set it if undefined', () => {
+      const NODE_V8_COVERAGE = process.env.NODE_V8_COVERAGE
+      process.env.NODE_V8_COVERAGE = undefined
+      process.argv = ['node', 'c8', '--foo=99', 'my-app', '--help']
+      const argv = buildYargs().parse(hideInstrumenteeArgs())
+      argv.tempDirectory.endsWith('/coverage/tmp').should.be.equal(true)
+      delete process.env.NODE_V8_COVERAGE
       process.env.NODE_V8_COVERAGE = NODE_V8_COVERAGE
     })
+    /** */
   })
 
   describe('--config', () => {