1// Copyright 2009 The Go Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style
3// license that can be found in the LICENSE file.
4
5// Package quick implements utility functions to help with black box testing.
6//
7// The testing/quick package is frozen and is not accepting new features.
8package quick
9
10import (
11	"flag"
12	"fmt"
13	"math"
14	"math/rand"
15	"reflect"
16	"strings"
17	"time"
18)
19
20var defaultMaxCount *int = flag.Int("quickchecks", 100, "The default number of iterations for each check")
21
22// A Generator can generate random values of its own type.
23type Generator interface {
24	// Generate returns a random instance of the type on which it is a
25	// method using the size as a size hint.
26	Generate(rand *rand.Rand, size int) reflect.Value
27}
28
29// randFloat32 generates a random float taking the full range of a float32.
30func randFloat32(rand *rand.Rand) float32 {
31	f := rand.Float64() * math.MaxFloat32
32	if rand.Int()&1 == 1 {
33		f = -f
34	}
35	return float32(f)
36}
37
38// randFloat64 generates a random float taking the full range of a float64.
39func randFloat64(rand *rand.Rand) float64 {
40	f := rand.Float64() * math.MaxFloat64
41	if rand.Int()&1 == 1 {
42		f = -f
43	}
44	return f
45}
46
47// randInt64 returns a random int64.
48func randInt64(rand *rand.Rand) int64 {
49	return int64(rand.Uint64())
50}
51
52// complexSize is the maximum length of arbitrary values that contain other
53// values.
54const complexSize = 50
55
56// Value returns an arbitrary value of the given type.
57// If the type implements the Generator interface, that will be used.
58// Note: To create arbitrary values for structs, all the fields must be exported.
59func Value(t reflect.Type, rand *rand.Rand) (value reflect.Value, ok bool) {
60	return sizedValue(t, rand, complexSize)
61}
62
63// sizedValue returns an arbitrary value of the given type. The size
64// hint is used for shrinking as a function of indirection level so
65// that recursive data structures will terminate.
66func sizedValue(t reflect.Type, rand *rand.Rand, size int) (value reflect.Value, ok bool) {
67	if m, ok := reflect.Zero(t).Interface().(Generator); ok {
68		return m.Generate(rand, size), true
69	}
70
71	v := reflect.New(t).Elem()
72	switch concrete := t; concrete.Kind() {
73	case reflect.Bool:
74		v.SetBool(rand.Int()&1 == 0)
75	case reflect.Float32:
76		v.SetFloat(float64(randFloat32(rand)))
77	case reflect.Float64:
78		v.SetFloat(randFloat64(rand))
79	case reflect.Complex64:
80		v.SetComplex(complex(float64(randFloat32(rand)), float64(randFloat32(rand))))
81	case reflect.Complex128:
82		v.SetComplex(complex(randFloat64(rand), randFloat64(rand)))
83	case reflect.Int16:
84		v.SetInt(randInt64(rand))
85	case reflect.Int32:
86		v.SetInt(randInt64(rand))
87	case reflect.Int64:
88		v.SetInt(randInt64(rand))
89	case reflect.Int8:
90		v.SetInt(randInt64(rand))
91	case reflect.Int:
92		v.SetInt(randInt64(rand))
93	case reflect.Uint16:
94		v.SetUint(uint64(randInt64(rand)))
95	case reflect.Uint32:
96		v.SetUint(uint64(randInt64(rand)))
97	case reflect.Uint64:
98		v.SetUint(uint64(randInt64(rand)))
99	case reflect.Uint8:
100		v.SetUint(uint64(randInt64(rand)))
101	case reflect.Uint:
102		v.SetUint(uint64(randInt64(rand)))
103	case reflect.Uintptr:
104		v.SetUint(uint64(randInt64(rand)))
105	case reflect.Map:
106		numElems := rand.Intn(size)
107		v.Set(reflect.MakeMap(concrete))
108		for i := 0; i < numElems; i++ {
109			key, ok1 := sizedValue(concrete.Key(), rand, size)
110			value, ok2 := sizedValue(concrete.Elem(), rand, size)
111			if !ok1 || !ok2 {
112				return reflect.Value{}, false
113			}
114			v.SetMapIndex(key, value)
115		}
116	case reflect.Ptr:
117		if rand.Intn(size) == 0 {
118			v.Set(reflect.Zero(concrete)) // Generate nil pointer.
119		} else {
120			elem, ok := sizedValue(concrete.Elem(), rand, size)
121			if !ok {
122				return reflect.Value{}, false
123			}
124			v.Set(reflect.New(concrete.Elem()))
125			v.Elem().Set(elem)
126		}
127	case reflect.Slice:
128		numElems := rand.Intn(size)
129		sizeLeft := size - numElems
130		v.Set(reflect.MakeSlice(concrete, numElems, numElems))
131		for i := 0; i < numElems; i++ {
132			elem, ok := sizedValue(concrete.Elem(), rand, sizeLeft)
133			if !ok {
134				return reflect.Value{}, false
135			}
136			v.Index(i).Set(elem)
137		}
138	case reflect.Array:
139		for i := 0; i < v.Len(); i++ {
140			elem, ok := sizedValue(concrete.Elem(), rand, size)
141			if !ok {
142				return reflect.Value{}, false
143			}
144			v.Index(i).Set(elem)
145		}
146	case reflect.String:
147		numChars := rand.Intn(complexSize)
148		codePoints := make([]rune, numChars)
149		for i := 0; i < numChars; i++ {
150			codePoints[i] = rune(rand.Intn(0x10ffff))
151		}
152		v.SetString(string(codePoints))
153	case reflect.Struct:
154		n := v.NumField()
155		// Divide sizeLeft evenly among the struct fields.
156		sizeLeft := size
157		if n > sizeLeft {
158			sizeLeft = 1
159		} else if n > 0 {
160			sizeLeft /= n
161		}
162		for i := 0; i < n; i++ {
163			elem, ok := sizedValue(concrete.Field(i).Type, rand, sizeLeft)
164			if !ok {
165				return reflect.Value{}, false
166			}
167			v.Field(i).Set(elem)
168		}
169	default:
170		return reflect.Value{}, false
171	}
172
173	return v, true
174}
175
176// A Config structure contains options for running a test.
177type Config struct {
178	// MaxCount sets the maximum number of iterations.
179	// If zero, MaxCountScale is used.
180	MaxCount int
181	// MaxCountScale is a non-negative scale factor applied to the
182	// default maximum.
183	// If zero, the default is unchanged.
184	MaxCountScale float64
185	// Rand specifies a source of random numbers.
186	// If nil, a default pseudo-random source will be used.
187	Rand *rand.Rand
188	// Values specifies a function to generate a slice of
189	// arbitrary reflect.Values that are congruent with the
190	// arguments to the function being tested.
191	// If nil, the top-level Value function is used to generate them.
192	Values func([]reflect.Value, *rand.Rand)
193}
194
195var defaultConfig Config
196
197// getRand returns the *rand.Rand to use for a given Config.
198func (c *Config) getRand() *rand.Rand {
199	if c.Rand == nil {
200		return rand.New(rand.NewSource(time.Now().UnixNano()))
201	}
202	return c.Rand
203}
204
205// getMaxCount returns the maximum number of iterations to run for a given
206// Config.
207func (c *Config) getMaxCount() (maxCount int) {
208	maxCount = c.MaxCount
209	if maxCount == 0 {
210		if c.MaxCountScale != 0 {
211			maxCount = int(c.MaxCountScale * float64(*defaultMaxCount))
212		} else {
213			maxCount = *defaultMaxCount
214		}
215	}
216
217	return
218}
219
220// A SetupError is the result of an error in the way that check is being
221// used, independent of the functions being tested.
222type SetupError string
223
224func (s SetupError) Error() string { return string(s) }
225
226// A CheckError is the result of Check finding an error.
227type CheckError struct {
228	Count int
229	In    []interface{}
230}
231
232func (s *CheckError) Error() string {
233	return fmt.Sprintf("#%d: failed on input %s", s.Count, toString(s.In))
234}
235
236// A CheckEqualError is the result CheckEqual finding an error.
237type CheckEqualError struct {
238	CheckError
239	Out1 []interface{}
240	Out2 []interface{}
241}
242
243func (s *CheckEqualError) Error() string {
244	return fmt.Sprintf("#%d: failed on input %s. Output 1: %s. Output 2: %s", s.Count, toString(s.In), toString(s.Out1), toString(s.Out2))
245}
246
247// Check looks for an input to f, any function that returns bool,
248// such that f returns false. It calls f repeatedly, with arbitrary
249// values for each argument. If f returns false on a given input,
250// Check returns that input as a *CheckError.
251// For example:
252//
253// 	func TestOddMultipleOfThree(t *testing.T) {
254// 		f := func(x int) bool {
255// 			y := OddMultipleOfThree(x)
256// 			return y%2 == 1 && y%3 == 0
257// 		}
258// 		if err := quick.Check(f, nil); err != nil {
259// 			t.Error(err)
260// 		}
261// 	}
262func Check(f interface{}, config *Config) error {
263	if config == nil {
264		config = &defaultConfig
265	}
266
267	fVal, fType, ok := functionAndType(f)
268	if !ok {
269		return SetupError("argument is not a function")
270	}
271
272	if fType.NumOut() != 1 {
273		return SetupError("function does not return one value")
274	}
275	if fType.Out(0).Kind() != reflect.Bool {
276		return SetupError("function does not return a bool")
277	}
278
279	arguments := make([]reflect.Value, fType.NumIn())
280	rand := config.getRand()
281	maxCount := config.getMaxCount()
282
283	for i := 0; i < maxCount; i++ {
284		err := arbitraryValues(arguments, fType, config, rand)
285		if err != nil {
286			return err
287		}
288
289		if !fVal.Call(arguments)[0].Bool() {
290			return &CheckError{i + 1, toInterfaces(arguments)}
291		}
292	}
293
294	return nil
295}
296
297// CheckEqual looks for an input on which f and g return different results.
298// It calls f and g repeatedly with arbitrary values for each argument.
299// If f and g return different answers, CheckEqual returns a *CheckEqualError
300// describing the input and the outputs.
301func CheckEqual(f, g interface{}, config *Config) error {
302	if config == nil {
303		config = &defaultConfig
304	}
305
306	x, xType, ok := functionAndType(f)
307	if !ok {
308		return SetupError("f is not a function")
309	}
310	y, yType, ok := functionAndType(g)
311	if !ok {
312		return SetupError("g is not a function")
313	}
314
315	if xType != yType {
316		return SetupError("functions have different types")
317	}
318
319	arguments := make([]reflect.Value, xType.NumIn())
320	rand := config.getRand()
321	maxCount := config.getMaxCount()
322
323	for i := 0; i < maxCount; i++ {
324		err := arbitraryValues(arguments, xType, config, rand)
325		if err != nil {
326			return err
327		}
328
329		xOut := toInterfaces(x.Call(arguments))
330		yOut := toInterfaces(y.Call(arguments))
331
332		if !reflect.DeepEqual(xOut, yOut) {
333			return &CheckEqualError{CheckError{i + 1, toInterfaces(arguments)}, xOut, yOut}
334		}
335	}
336
337	return nil
338}
339
340// arbitraryValues writes Values to args such that args contains Values
341// suitable for calling f.
342func arbitraryValues(args []reflect.Value, f reflect.Type, config *Config, rand *rand.Rand) (err error) {
343	if config.Values != nil {
344		config.Values(args, rand)
345		return
346	}
347
348	for j := 0; j < len(args); j++ {
349		var ok bool
350		args[j], ok = Value(f.In(j), rand)
351		if !ok {
352			err = SetupError(fmt.Sprintf("cannot create arbitrary value of type %s for argument %d", f.In(j), j))
353			return
354		}
355	}
356
357	return
358}
359
360func functionAndType(f interface{}) (v reflect.Value, t reflect.Type, ok bool) {
361	v = reflect.ValueOf(f)
362	ok = v.Kind() == reflect.Func
363	if !ok {
364		return
365	}
366	t = v.Type()
367	return
368}
369
370func toInterfaces(values []reflect.Value) []interface{} {
371	ret := make([]interface{}, len(values))
372	for i, v := range values {
373		ret[i] = v.Interface()
374	}
375	return ret
376}
377
378func toString(interfaces []interface{}) string {
379	s := make([]string, len(interfaces))
380	for i, v := range interfaces {
381		s[i] = fmt.Sprintf("%#v", v)
382	}
383	return strings.Join(s, ", ")
384}
385