gostub: adding docs on SetEnv (#10)

README.md

@@ -25,7 +25,7 @@ static variable, use the Stub function:
 var configFile = "config.json"
 
 func GetConfig() ([]byte, error) {
-  return ioutil.ReadFile(configFile)
+    return ioutil.ReadFile(configFile)
 }
 
 // Test code
@@ -42,15 +42,15 @@ the static function, and using that local variable to call the static function:
 var timeNow = time.Now
 
 func GetDate() int {
-	return timeNow().Day()
+    return timeNow().Day()
 }
 ```
 
 You can test this by using gostub to stub the timeNow variable:
 
 ```go
 stubs := gostub.Stub(&timeNow, func() time.Time {
-  return time.Date(2015, 6, 1, 0, 0, 0, 0, time.UTC)
+    return time.Date(2015, 6, 1, 0, 0, 0, 0, time.UTC)
 })
 defer stubs.Reset()
 
@@ -75,6 +75,14 @@ var osHostname = osHostname
 stubs := gostub.StubFunc(&osHostname, "fakehost", nil)
 defer stubs.Reset()
 ```
+StubEnv can be used to setup environment variables for tests, and the
+environment values are reset to their original values upon Reset:
+
+```go
+stubs := gostub.New()
+stubs.SetEnv("GOSTUB_VAR", "test_value")
+defer stubs.Reset()
+```
 
 The Reset method should be deferred to run at the end of the test to reset all
 stubbed variables back to their original values.

doc.go

@@ -4,6 +4,7 @@ original value once the test has been run.
 
 This can be used to stub static variables as well as static functions. To
 stub a static variable, use the Stub function:
+
   var configFile = "config.json"
 
   func GetConfig() ([]byte, error) {
@@ -46,6 +47,13 @@ StubFunc can also be used to stub functions that return multiple values:
   stubs := gostub.StubFunc(&osHostname, "fakehost", nil)
   defer stubs.Reset()
 
+StubEnv can be used to setup environment variables for tests, and the environment
+values are reset to their original values upon Reset:
+
+  stubs := gostub.New()
+  stubs.SetEnv("GOSTUB_VAR", "test_value")
+  defer stubs.Reset()
+
 The Reset method should be deferred to run at the end of the test to reset
 all stubbed variables back to their original values.
 
@@ -75,4 +83,5 @@ and a value which can be assigned to the variable.
 */
 package gostub
 
+// FIXME: godocdown no longer works with go syntax highlighting.
 //go:generate godocdown -template README.md.tmpl --output=README.md