feat(httpx): improve testing using the fakefiller (#649)
This diff extracts the fakefiller inside of internal/ooapi (a currently unused package) into its own package. The fakefiller knows how to fill many fields that are typically shared as data structures across processes. It is not perfect in that it cannot fill logger or http client fields, but still helps with better filling and testing. So, here we're using the fakefiller to improve testing of httpx and, nicely enough, we've already catched a bug in the way in which APIClientTemplate.Build misses to forward Authorization from the original template. Yay! Work part of https://github.com/ooni/probe/issues/1951
This commit is contained in:
Simone Basso
GitHub
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// Package fakefill contains code to fill structs for testing.
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//
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// This package is quite limited in scope and we can fill only the
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// structures you typically send over as JSONs.
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//
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// As part of future work, we aim to investigate whether we can
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// replace this implementation with https://go.dev/blog/fuzz-beta.
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package fakefill
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import (
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"math/rand"
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"reflect"
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"sync"
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"time"
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)
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// Filler fills specific data structures with random data. The only
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// exception to this behaviour is time.Time, which is instead filled
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// with the current time plus a small random number of seconds.
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//
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// We use this implementation to initialize data in our model. The code
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// has been written with that in mind. It will require some hammering in
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// case we extend the model with new field types.
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//
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// Caveat: this kind of fillter does not support filling interfaces
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// and channels and other complex types. The current behavior when this
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// kind of data types is encountered is to just ignore them.
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type Filler struct {
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// mu provides mutual exclusion
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mu sync.Mutex
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// Now is OPTIONAL and allows to mock the current time
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Now func() time.Time
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// rnd is the random number generator and is
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// automatically initialized on first use
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rnd *rand.Rand
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}
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func (ff *Filler) getRandLocked() *rand.Rand {
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if ff.rnd == nil {
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now := time.Now
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if ff.Now != nil {
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now = ff.Now
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}
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ff.rnd = rand.New(rand.NewSource(now().UnixNano()))
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}
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return ff.rnd
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}
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func (ff *Filler) getRandomString() string {
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defer ff.mu.Unlock()
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ff.mu.Lock()
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rnd := ff.getRandLocked()
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n := rnd.Intn(63) + 1
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// See https://stackoverflow.com/a/31832326
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var letterRunes = []rune("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ")
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b := make([]rune, n)
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for i := range b {
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b[i] = letterRunes[rnd.Intn(len(letterRunes))]
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}
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return string(b)
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}
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func (ff *Filler) getRandomInt64() int64 {
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defer ff.mu.Unlock()
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ff.mu.Lock()
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rnd := ff.getRandLocked()
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return rnd.Int63()
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}
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func (ff *Filler) getRandomBool() bool {
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defer ff.mu.Unlock()
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ff.mu.Lock()
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rnd := ff.getRandLocked()
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return rnd.Float64() >= 0.5
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}
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func (ff *Filler) getRandomSmallPositiveInt() int {
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defer ff.mu.Unlock()
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ff.mu.Lock()
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rnd := ff.getRandLocked()
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return int(rnd.Int63n(8)) + 1 // safe cast
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}
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func (ff *Filler) doFill(v reflect.Value) {
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for v.Type().Kind() == reflect.Ptr {
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if v.IsNil() {
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// if the pointer is nil, allocate an element
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v.Set(reflect.New(v.Type().Elem()))
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}
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// switch to the element
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v = v.Elem()
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}
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switch v.Type().Kind() {
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case reflect.String:
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v.SetString(ff.getRandomString())
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case reflect.Int64:
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v.SetInt(ff.getRandomInt64())
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case reflect.Bool:
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v.SetBool(ff.getRandomBool())
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case reflect.Struct:
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if v.Type().String() == "time.Time" {
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// Implementation note: we treat the time specially
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// and we avoid attempting to set its fields.
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v.Set(reflect.ValueOf(time.Now().Add(
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time.Duration(ff.getRandomSmallPositiveInt()) * time.Second)))
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return
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}
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for idx := 0; idx < v.NumField(); idx++ {
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ff.doFill(v.Field(idx)) // visit all fields
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}
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case reflect.Slice:
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kind := v.Type().Elem()
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total := ff.getRandomSmallPositiveInt()
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for idx := 0; idx < total; idx++ {
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value := reflect.New(kind) // make a new element
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ff.doFill(value)
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v.Set(reflect.Append(v, value.Elem())) // append to slice
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}
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case reflect.Map:
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if v.Type().Key().Kind() != reflect.String {
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panic("fakefill: we only support string key types")
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}
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v.Set(reflect.MakeMap(v.Type())) // we need to init the map
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total := ff.getRandomSmallPositiveInt()
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kind := v.Type().Elem()
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for idx := 0; idx < total; idx++ {
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value := reflect.New(kind)
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ff.doFill(value)
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v.SetMapIndex(reflect.ValueOf(ff.getRandomString()), value.Elem())
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}
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}
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}
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// Fill fills the input structure or pointer with random data.
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func (ff *Filler) Fill(in interface{}) {
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ff.doFill(reflect.ValueOf(in))
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}
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@@ -0,0 +1,91 @@
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package fakefill
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import (
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"testing"
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"time"
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)
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// exampleStructure is an example structure we fill.
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type exampleStructure struct {
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CategoryCodes string
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CountryCode string
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Enabled bool
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MaxResults int64
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Now time.Time
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}
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func TestFakeFillWorksWithCustomTime(t *testing.T) {
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var req *exampleStructure
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ff := &Filler{
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Now: func() time.Time {
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return time.Date(1992, time.January, 24, 17, 53, 0, 0, time.UTC)
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},
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}
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ff.Fill(&req)
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if req == nil {
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t.Fatal("we expected non nil here")
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}
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}
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func TestFakeFillAllocatesIntoAPointerToPointer(t *testing.T) {
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var req *exampleStructure
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ff := &Filler{}
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ff.Fill(&req)
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if req == nil {
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t.Fatal("we expected non nil here")
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}
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}
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func TestFakeFillAllocatesIntoAMapLikeWithStringKeys(t *testing.T) {
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var resp map[string]*exampleStructure
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ff := &Filler{}
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ff.Fill(&resp)
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if resp == nil {
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t.Fatal("we expected non nil here")
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}
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if len(resp) < 1 {
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t.Fatal("we expected some data here")
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}
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for _, value := range resp {
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if value == nil {
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t.Fatal("expected non-nil here")
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}
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}
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}
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func TestFakeFillAllocatesIntoAMapLikeWithNonStringKeys(t *testing.T) {
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var panicmsg string
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func() {
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defer func() {
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if v := recover(); v != nil {
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panicmsg = v.(string)
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}
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}()
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var resp map[int64]*exampleStructure
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ff := &Filler{}
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ff.Fill(&resp)
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if resp != nil {
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t.Fatal("we expected nil here")
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}
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}()
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if panicmsg != "fakefill: we only support string key types" {
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t.Fatal("unexpected panic message", panicmsg)
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}
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}
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func TestFakeFillAllocatesIntoASlice(t *testing.T) {
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var resp *[]*exampleStructure
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ff := &Filler{}
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ff.Fill(&resp)
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if resp == nil {
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t.Fatal("we expected non nil here")
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}
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if len(*resp) < 1 {
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t.Fatal("we expected some data here")
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}
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for _, entry := range *resp {
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if entry == nil {
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t.Fatal("expected non-nil here")
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}
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}
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}
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