rewrite source-map-cache tests

Use source-map-fixtures to get a fixture file with an inline source map. Add a
script to generate a coverage report for this specific fixture. Rewrite tests to
use the fixture, without (too much) hardcoding of values.

This will make it easier to upgrade the fixture in the future, as well as
regenerate the coverage report.

It does break the babel tests. Will fix that in the next commit.

package.json

@@ -17,7 +17,8 @@
         "bin",
         "coverage",
         "test/nyc-test.js",
-        "test/source-map-cache.js"
+        "test/source-map-cache.js",
+        "test/fixtures/_generateCoverage.js"
       ]
     }
   },
@@ -63,6 +64,7 @@
     "babel-preset-es2015": "^6.1.18",
     "chai": "^3.0.0",
     "sinon": "^1.15.3",
+    "source-map-fixtures": "^0.1.0",
     "standard": "^5.2.1",
     "tap": "^1.3.4"
   },

test/fixtures/_generateCoverage.js

@@ -0,0 +1,48 @@
+'use strict'
+
+// Generates the test/fixtures/coverage.js file, not otherwise used in the
+// tests.
+
+var fs = require('fs')
+var path = require('path')
+
+var _ = require('lodash')
+var rimraf = require('rimraf')
+
+var NYC = require('../../')
+
+// Load the 'branching' source map fixture.
+var fixture = require('source-map-fixtures').inline('branching')
+
+// Prevent pollution from earlier nyc runs.
+var tempDirectory = path.join(__dirname, '.nyc_output')
+rimraf.sync(tempDirectory)
+
+// Inject nyc into this process.
+var nyc = (new NYC({
+  cwd: path.join(__dirname, '..', '..'),
+  tempDirectory: tempDirectory
+})).wrap()
+// Override the exclude option, source-map-fixtures is inside node_modules but
+// should not be excluded when generating the coverage report.
+nyc.exclude = []
+
+// Require the fixture so nyc can instrument it, then run it so there's code
+// coverage.
+fixture.require().run()
+
+// Write the coverage file so reports can be loaded.
+nyc.writeCoverageFile()
+
+var reports = _.values(nyc._loadReports()[0])
+if (reports.length !== 1) {
+  console.error('Expected 1 report to be generated, got ' + reports.length)
+  process.exit(1)
+}
+
+var coverage = reports[0]
+fs.writeFileSync(
+  path.join(__dirname, 'coverage.js'),
+  '// Generated using node test/fixtures/_generateCoverage.js\n' +
+  'exports[' + JSON.stringify(coverage.path) + '] = ' + JSON.stringify(coverage, null, 2) + '\n')
+console.log('Written coverage report.')