Add test runner

Author: bobzhang

jscomp/build_tests/customize_namespace/input.js

@@ -0,0 +1,8 @@
+
+//@ts-check
+
+var cp = require('child_process')
+var assert = require('assert')
+cp.execSync(`bsb -make-world`, {cwd : __dirname, encoding : 'utf8'})
+
+assert.equal(require('./src/demo.bs').v,5)

jscomp/build_tests/customize_namespace/src/demo.ml

@@ -1,4 +1,4 @@
 
 
 let () = Js.log "Hello, BuckleScript"
-let () = Js.log (Depx.Demo.v + Depb.Demo.v)
+let v = Depx.Demo.v + Depb.Demo.v