text_test.go

     1  // Copyright 2024 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 rand_test
     6  
     7  import (
     8  	"crypto/rand"
     9  	"fmt"
    10  	"testing"
    11  )
    12  
    13  func TestText(t *testing.T) {
    14  	set := make(map[string]struct{}) // hold every string produced
    15  	var indexSet [26]map[rune]int    // hold every char produced at every position
    16  	for i := range indexSet {
    17  		indexSet[i] = make(map[rune]int)
    18  	}
    19  
    20  	// not getting a char in a position: (31/32)¹⁰⁰⁰ = 1.6e-14
    21  	// test completion within 1000 rounds: (1-(31/32)¹⁰⁰⁰)²⁶ = 0.9999999999996
    22  	// empirically, this should complete within 400 rounds = 0.999921
    23  	rounds := 1000
    24  	var done bool
    25  	for range rounds {
    26  		s := rand.Text()
    27  		if len(s) != 26 {
    28  			t.Errorf("len(Text()) = %d, want = 26", len(s))
    29  		}
    30  		for i, r := range s {
    31  			if ('A' > r || r > 'Z') && ('2' > r || r > '7') {
    32  				t.Errorf("Text()[%d] = %v, outside of base32 alphabet", i, r)
    33  			}
    34  		}
    35  		if _, ok := set[s]; ok {
    36  			t.Errorf("Text() = %s, duplicate of previously produced string", s)
    37  		}
    38  		set[s] = struct{}{}
    39  
    40  		done = true
    41  		for i, r := range s {
    42  			indexSet[i][r]++
    43  			if len(indexSet[i]) != 32 {
    44  				done = false
    45  			}
    46  		}
    47  		if done {
    48  			break
    49  		}
    50  	}
    51  	if !done {
    52  		t.Errorf("failed to produce every char at every index after %d rounds", rounds)
    53  		indexSetTable(t, indexSet)
    54  	}
    55  }
    56  
    57  func indexSetTable(t *testing.T, indexSet [26]map[rune]int) {
    58  	alphabet := "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567"
    59  	line := "   "
    60  	for _, r := range alphabet {
    61  		line += fmt.Sprintf(" %3s", string(r))
    62  	}
    63  	t.Log(line)
    64  	for i, set := range indexSet {
    65  		line = fmt.Sprintf("%2d:", i)
    66  		for _, r := range alphabet {
    67  			line += fmt.Sprintf(" %3d", set[r])
    68  		}
    69  		t.Log(line)
    70  	}
    71  }
    72
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