github.com/whtcorpsinc/MilevaDB-Prod@v0.0.0-20211104133533-f57f4be3b597/dbs/memristed/memex/rand_test.go (about)

     1  // Copyright 2020 WHTCORPS INC, Inc.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // See the License for the specific language governing permissions and
    12  // limitations under the License.
    13  
    14  package memex
    15  
    16  import (
    17  	"time"
    18  
    19  	"github.com/whtcorpsinc/check"
    20  )
    21  
    22  func (s *testExpressionSuite) TestRandWithTime(c *check.C) {
    23  	rng1 := NewWithTime()
    24  	// NOTE: On windows platform, this Sleep is necessary. Because time.Now() is
    25  	// imprecise, calling UnixNano() twice returns the same value. We have to make
    26  	// sure the elapsed time is longer than 1ms to get different values.
    27  	time.Sleep(time.Millisecond)
    28  	rng2 := NewWithTime()
    29  	got1 := rng1.Gen()
    30  	got2 := rng2.Gen()
    31  	c.Assert(got1 < 1.0, check.IsTrue)
    32  	c.Assert(got1 >= 0.0, check.IsTrue)
    33  	c.Assert(got1 != rng1.Gen(), check.IsTrue)
    34  	c.Assert(got2 < 1.0, check.IsTrue)
    35  	c.Assert(got2 >= 0.0, check.IsTrue)
    36  	c.Assert(got2 != rng2.Gen(), check.IsTrue)
    37  	c.Assert(got1 != got2, check.IsTrue)
    38  }
    39  
    40  func (s *testExpressionSuite) TestRandWithSeed(c *check.C) {
    41  	tests := [4]struct {
    42  		seed  int64
    43  		once  float64
    44  		twice float64
    45  	}{{0, 0.15522042769493574, 0.620881741513388},
    46  		{1, 0.40540353712197724, 0.8716141803857071},
    47  		{-1, 0.9050373219931845, 0.37014932126752037},
    48  		{9223372036854775807, 0.9050373219931845, 0.37014932126752037}}
    49  	for _, test := range tests {
    50  		rng := NewWithSeed(test.seed)
    51  		got1 := rng.Gen()
    52  		c.Assert(got1 == test.once, check.IsTrue)
    53  		got2 := rng.Gen()
    54  		c.Assert(got2 == test.twice, check.IsTrue)
    55  	}
    56  }