github.com/c12o16h1/go/src@v0.0.0-20200114212001-5a151c0f00ed/hash/maphash/maphash_test.go (about)

     1  // Copyright 2019 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 maphash
     6  
     7  import (
     8  	"hash"
     9  	"testing"
    10  )
    11  
    12  func TestUnseededHash(t *testing.T) {
    13  	m := map[uint64]struct{}{}
    14  	for i := 0; i < 1000; i++ {
    15  		h := new(Hash)
    16  		m[h.Sum64()] = struct{}{}
    17  	}
    18  	if len(m) < 900 {
    19  		t.Errorf("empty hash not sufficiently random: got %d, want 1000", len(m))
    20  	}
    21  }
    22  
    23  func TestSeededHash(t *testing.T) {
    24  	s := MakeSeed()
    25  	m := map[uint64]struct{}{}
    26  	for i := 0; i < 1000; i++ {
    27  		h := new(Hash)
    28  		h.SetSeed(s)
    29  		m[h.Sum64()] = struct{}{}
    30  	}
    31  	if len(m) != 1 {
    32  		t.Errorf("seeded hash is random: got %d, want 1", len(m))
    33  	}
    34  }
    35  
    36  func TestHashGrouping(t *testing.T) {
    37  	b := []byte("foo")
    38  	h1 := new(Hash)
    39  	h2 := new(Hash)
    40  	h2.SetSeed(h1.Seed())
    41  	h1.Write(b)
    42  	for _, x := range b {
    43  		err := h2.WriteByte(x)
    44  		if err != nil {
    45  			t.Fatalf("WriteByte: %v", err)
    46  		}
    47  	}
    48  	if h1.Sum64() != h2.Sum64() {
    49  		t.Errorf("hash of \"foo\" and \"f\",\"o\",\"o\" not identical")
    50  	}
    51  }
    52  
    53  func TestHashBytesVsString(t *testing.T) {
    54  	s := "foo"
    55  	b := []byte(s)
    56  	h1 := new(Hash)
    57  	h2 := new(Hash)
    58  	h2.SetSeed(h1.Seed())
    59  	n1, err1 := h1.WriteString(s)
    60  	if n1 != len(s) || err1 != nil {
    61  		t.Fatalf("WriteString(s) = %d, %v, want %d, nil", n1, err1, len(s))
    62  	}
    63  	n2, err2 := h2.Write(b)
    64  	if n2 != len(b) || err2 != nil {
    65  		t.Fatalf("Write(b) = %d, %v, want %d, nil", n2, err2, len(b))
    66  	}
    67  	if h1.Sum64() != h2.Sum64() {
    68  		t.Errorf("hash of string and bytes not identical")
    69  	}
    70  }
    71  
    72  func TestHashHighBytes(t *testing.T) {
    73  	// See issue 34925.
    74  	const N = 10
    75  	m := map[uint64]struct{}{}
    76  	for i := 0; i < N; i++ {
    77  		h := new(Hash)
    78  		h.WriteString("foo")
    79  		m[h.Sum64()>>32] = struct{}{}
    80  	}
    81  	if len(m) < N/2 {
    82  		t.Errorf("from %d seeds, wanted at least %d different hashes; got %d", N, N/2, len(m))
    83  	}
    84  }
    85  
    86  // Make sure a Hash implements the hash.Hash and hash.Hash64 interfaces.
    87  var _ hash.Hash = &Hash{}
    88  var _ hash.Hash64 = &Hash{}