panic: runtime error: invalid memory address or nil pointer dereference

[peterbe]

I bet I'm doing something wrong being a noob and all but it seems like it should work:

:~/dev/GO/autocompeter (integration-test +%)$ go test -v
=== RUN TestHandleIndexReturnsWithStatusOK
--- FAIL: TestHandleIndexReturnsWithStatusOK (0.00s)
panic: runtime error: invalid memory address or nil pointer dereference [recovered]
    panic: runtime error: invalid memory address or nil pointer dereference
[signal 0xb code=0x1 addr=0xc8 pc=0xf2fba]

goroutine 5 [running]:
testing.func·006()
    /opt/boxen/homebrew/Cellar/go/1.4.1/libexec/src/testing/testing.go:441 +0x181
github.com/unrolled/render.(*Render).HTML(0x0, 0x823440, 0xc20800a0c0, 0xc8, 0x420370, 0x5, 0x0, 0x0, 0x0, 0x0, ...)
    /Users/peterbe/dev/GO/src/github.com/unrolled/render/render.go:249 +0x2a
_/Users/peterbe/dev/GO/autocompeter.IndexHandler(0x823440, 0xc20800a0c0, 0xc20801e5b0)
    /Users/peterbe/dev/GO/autocompeter/main.go:80 +0x8a
_/Users/peterbe/dev/GO/autocompeter.TestHandleIndexReturnsWithStatusOK(0xc20806a090)
    /Users/peterbe/dev/GO/autocompeter/main_test.go:13 +0x175
testing.tRunner(0xc20806a090, 0x752690)
    /opt/boxen/homebrew/Cellar/go/1.4.1/libexec/src/testing/testing.go:447 +0xbf
created by testing.RunTests
    /opt/boxen/homebrew/Cellar/go/1.4.1/libexec/src/testing/testing.go:555 +0xa8b

goroutine 1 [chan receive]:
testing.RunTests(0x5197e8, 0x752690, 0x1, 0x1, 0x75d301)
    /opt/boxen/homebrew/Cellar/go/1.4.1/libexec/src/testing/testing.go:556 +0xad6
testing.(*M).Run(0xc20802a0f0, 0x764780)
    /opt/boxen/homebrew/Cellar/go/1.4.1/libexec/src/testing/testing.go:485 +0x6c
main.main()
    _/Users/peterbe/dev/GO/autocompeter/_test/_testmain.go:52 +0x1d5
exit status 2
FAIL    _/Users/peterbe/dev/GO/autocompeter 0.021s

The test is extremely simple so far:

package main

import (
    "net/http"
    "net/http/httptest"
    "testing"
)

func TestHandleIndexReturnsWithStatusOK(t *testing.T) {
    request, _ := http.NewRequest("GET", "/", nil)
    response := httptest.NewRecorder()

    IndexHandler(response, request)

    if response.Code != http.StatusOK {
        t.Fatalf("Non-expected status code%v:\n\tbody: %v", "200", response.Code)
    }
}

And in main.go there's a bunch of other stuff but the things that matter should be:

package main
import "github.com/unrolled/render"

func IndexHandler(w http.ResponseWriter, req *http.Request) {
    // this assumes there's a `templates/index.tmpl` file
    renderer.HTML(w, http.StatusOK, "index", nil)
}

var (
    renderer   *render.Render
    debug      = true
)

func main() {
        ...
    renderer = render.New(render.Options{
        IndentJSON:    debug,
        IsDevelopment: debug,
    })
        ...
        mux := mux.NewRouter()
    mux.HandleFunc("/", IndexHandler).Methods("GET", "HEAD")

    n := negroni.Classic()
    n.UseHandler(mux)
    n.Run(fmt.Sprintf(":%d", port))

}

Perhaps that's now how you're supposed to do testing of http handlers.

[unrolled]

Hey Peter, you code looks good, but we need to initial the renderer variable before the handler can be called in your test.

func TestHandleIndexReturnsWithStatusOK(t *testing.T) {
    request, _ := http.NewRequest("GET", "/", nil)
    response := httptest.NewRecorder()

    // Since main isn't called for the test, we need to initialize the renderer var manually.
    renderer = render.New(render.Options{
        IndentJSON:    true,
        IsDevelopment: true,
    })

    IndexHandler(response, request)

    if response.Code != http.StatusOK {
        t.Fatalf("Non-expected status code%v:\n\tbody: %v", "200", response.Code)
    }
}

If you don't have to much customization, you could initial the renderer when you declare it:

var (
    debug    = true
    renderer = render.New(render.Options{
        IndentJSON:    debug,
        IsDevelopment: debug,
    })
)

With that, you wouldn't need to change your test code.

Let me know if this helps!

[peterbe]

Yay! That works. Thing is, I want the debug to come in from a flag which I have in my main(). E.g. flag.BoolVar(&debug, "debug", false, "Debug mode")

So, instead I made a default renderer that does not use debug and then I override it in main() later. Now I get working tests and ability to use the debug when running the server on the command line.

var (
    debug      = true
    renderer  = render.New()
)

func main() {
    flag.BoolVar(&debug, "debug", false, "Debug mode")
    renderer = render.New(render.Options{
        IndentJSON:    debug,
        IsDevelopment: debug,
    })
}

[unrolled]

👍