github.com/codingfuture/orig-energi3@v0.8.4/swarm/storage/feed/lookup/lookup_test.go (about)

     1  // Copyright 2018 The go-ethereum Authors
     2  // This file is part of the go-ethereum library.
     3  //
     4  // The go-ethereum library is free software: you can redistribute it and/or modify
     5  // it under the terms of the GNU Lesser General Public License as published by
     6  // the Free Software Foundation, either version 3 of the License, or
     7  // (at your option) any later version.
     8  //
     9  // The go-ethereum library is distributed in the hope that it will be useful,
    10  // but WITHOUT ANY WARRANTY; without even the implied warranty of
    11  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
    12  // GNU Lesser General Public License for more details.
    13  //
    14  // You should have received a copy of the GNU Lesser General Public License
    15  // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
    16  
    17  package lookup_test
    18  
    19  import (
    20  	"fmt"
    21  	"math/rand"
    22  	"testing"
    23  
    24  	"github.com/ethereum/go-ethereum/swarm/log"
    25  	"github.com/ethereum/go-ethereum/swarm/storage/feed/lookup"
    26  )
    27  
    28  type Data struct {
    29  	Payload uint64
    30  	Time    uint64
    31  }
    32  
    33  type Store map[lookup.EpochID]*Data
    34  
    35  func write(store Store, epoch lookup.Epoch, value *Data) {
    36  	log.Debug("Write: %d-%d, value='%d'\n", epoch.Base(), epoch.Level, value.Payload)
    37  	store[epoch.ID()] = value
    38  }
    39  
    40  func update(store Store, last lookup.Epoch, now uint64, value *Data) lookup.Epoch {
    41  	epoch := lookup.GetNextEpoch(last, now)
    42  
    43  	write(store, epoch, value)
    44  
    45  	return epoch
    46  }
    47  
    48  const Day = 60 * 60 * 24
    49  const Year = Day * 365
    50  const Month = Day * 30
    51  
    52  func makeReadFunc(store Store, counter *int) lookup.ReadFunc {
    53  	return func(epoch lookup.Epoch, now uint64) (interface{}, error) {
    54  		*counter++
    55  		data := store[epoch.ID()]
    56  		var valueStr string
    57  		if data != nil {
    58  			valueStr = fmt.Sprintf("%d", data.Payload)
    59  		}
    60  		log.Debug("Read: %d-%d, value='%s'\n", epoch.Base(), epoch.Level, valueStr)
    61  		if data != nil && data.Time <= now {
    62  			return data, nil
    63  		}
    64  		return nil, nil
    65  	}
    66  }
    67  
    68  func TestLookup(t *testing.T) {
    69  
    70  	store := make(Store)
    71  	readCount := 0
    72  	readFunc := makeReadFunc(store, &readCount)
    73  
    74  	// write an update every month for 12 months 3 years ago and then silence for two years
    75  	now := uint64(1533799046)
    76  	var epoch lookup.Epoch
    77  
    78  	var lastData *Data
    79  	for i := uint64(0); i < 12; i++ {
    80  		t := uint64(now - Year*3 + i*Month)
    81  		data := Data{
    82  			Payload: t, //our "payload" will be the timestamp itself.
    83  			Time:    t,
    84  		}
    85  		epoch = update(store, epoch, t, &data)
    86  		lastData = &data
    87  	}
    88  
    89  	// try to get the last value
    90  
    91  	value, err := lookup.Lookup(now, lookup.NoClue, readFunc)
    92  	if err != nil {
    93  		t.Fatal(err)
    94  	}
    95  
    96  	readCountWithoutHint := readCount
    97  
    98  	if value != lastData {
    99  		t.Fatalf("Expected lookup to return the last written value: %v. Got %v", lastData, value)
   100  	}
   101  
   102  	// reset the read count for the next test
   103  	readCount = 0
   104  	// Provide a hint to get a faster lookup. In particular, we give the exact location of the last update
   105  	value, err = lookup.Lookup(now, epoch, readFunc)
   106  	if err != nil {
   107  		t.Fatal(err)
   108  	}
   109  
   110  	if value != lastData {
   111  		t.Fatalf("Expected lookup to return the last written value: %v. Got %v", lastData, value)
   112  	}
   113  
   114  	if readCount > readCountWithoutHint {
   115  		t.Fatalf("Expected lookup to complete with fewer or same reads than %d since we provided a hint. Did %d reads.", readCountWithoutHint, readCount)
   116  	}
   117  
   118  	// try to get an intermediate value
   119  	// if we look for a value in now - Year*3 + 6*Month, we should get that value
   120  	// Since the "payload" is the timestamp itself, we can check this.
   121  
   122  	expectedTime := now - Year*3 + 6*Month
   123  
   124  	value, err = lookup.Lookup(expectedTime, lookup.NoClue, readFunc)
   125  	if err != nil {
   126  		t.Fatal(err)
   127  	}
   128  
   129  	data, ok := value.(*Data)
   130  
   131  	if !ok {
   132  		t.Fatal("Expected value to contain data")
   133  	}
   134  
   135  	if data.Time != expectedTime {
   136  		t.Fatalf("Expected value timestamp to be %d, got %d", data.Time, expectedTime)
   137  	}
   138  
   139  }
   140  
   141  func TestOneUpdateAt0(t *testing.T) {
   142  
   143  	store := make(Store)
   144  	readCount := 0
   145  
   146  	readFunc := makeReadFunc(store, &readCount)
   147  	now := uint64(1533903729)
   148  
   149  	var epoch lookup.Epoch
   150  	data := Data{
   151  		Payload: 79,
   152  		Time:    0,
   153  	}
   154  	update(store, epoch, 0, &data)
   155  
   156  	value, err := lookup.Lookup(now, lookup.NoClue, readFunc)
   157  	if err != nil {
   158  		t.Fatal(err)
   159  	}
   160  	if value != &data {
   161  		t.Fatalf("Expected lookup to return the last written value: %v. Got %v", data, value)
   162  	}
   163  }
   164  
   165  // Tests the update is found even when a bad hint is given
   166  func TestBadHint(t *testing.T) {
   167  
   168  	store := make(Store)
   169  	readCount := 0
   170  
   171  	readFunc := makeReadFunc(store, &readCount)
   172  	now := uint64(1533903729)
   173  
   174  	var epoch lookup.Epoch
   175  	data := Data{
   176  		Payload: 79,
   177  		Time:    0,
   178  	}
   179  
   180  	// place an update for t=1200
   181  	update(store, epoch, 1200, &data)
   182  
   183  	// come up with some evil hint
   184  	badHint := lookup.Epoch{
   185  		Level: 18,
   186  		Time:  1200000000,
   187  	}
   188  
   189  	value, err := lookup.Lookup(now, badHint, readFunc)
   190  	if err != nil {
   191  		t.Fatal(err)
   192  	}
   193  	if value != &data {
   194  		t.Fatalf("Expected lookup to return the last written value: %v. Got %v", data, value)
   195  	}
   196  }
   197  
   198  func TestLookupFail(t *testing.T) {
   199  
   200  	store := make(Store)
   201  	readCount := 0
   202  
   203  	readFunc := makeReadFunc(store, &readCount)
   204  	now := uint64(1533903729)
   205  
   206  	// don't write anything and try to look up.
   207  	// we're testing we don't get stuck in a loop
   208  
   209  	value, err := lookup.Lookup(now, lookup.NoClue, readFunc)
   210  	if err != nil {
   211  		t.Fatal(err)
   212  	}
   213  	if value != nil {
   214  		t.Fatal("Expected value to be nil, since the update should've failed")
   215  	}
   216  
   217  	expectedReads := now/(1<<lookup.HighestLevel) + 1
   218  	if uint64(readCount) != expectedReads {
   219  		t.Fatalf("Expected lookup to fail after %d reads. Did %d reads.", expectedReads, readCount)
   220  	}
   221  }
   222  
   223  func TestHighFreqUpdates(t *testing.T) {
   224  
   225  	store := make(Store)
   226  	readCount := 0
   227  
   228  	readFunc := makeReadFunc(store, &readCount)
   229  	now := uint64(1533903729)
   230  
   231  	// write an update every second for the last 1000 seconds
   232  	var epoch lookup.Epoch
   233  
   234  	var lastData *Data
   235  	for i := uint64(0); i <= 994; i++ {
   236  		T := uint64(now - 1000 + i)
   237  		data := Data{
   238  			Payload: T, //our "payload" will be the timestamp itself.
   239  			Time:    T,
   240  		}
   241  		epoch = update(store, epoch, T, &data)
   242  		lastData = &data
   243  	}
   244  
   245  	value, err := lookup.Lookup(lastData.Time, lookup.NoClue, readFunc)
   246  	if err != nil {
   247  		t.Fatal(err)
   248  	}
   249  
   250  	if value != lastData {
   251  		t.Fatalf("Expected lookup to return the last written value: %v. Got %v", lastData, value)
   252  	}
   253  
   254  	readCountWithoutHint := readCount
   255  	// reset the read count for the next test
   256  	readCount = 0
   257  	// Provide a hint to get a faster lookup. In particular, we give the exact location of the last update
   258  	value, err = lookup.Lookup(now, epoch, readFunc)
   259  	if err != nil {
   260  		t.Fatal(err)
   261  	}
   262  
   263  	if value != lastData {
   264  		t.Fatalf("Expected lookup to return the last written value: %v. Got %v", lastData, value)
   265  	}
   266  
   267  	if readCount > readCountWithoutHint {
   268  		t.Fatalf("Expected lookup to complete with fewer or equal reads than %d since we provided a hint. Did %d reads.", readCountWithoutHint, readCount)
   269  	}
   270  
   271  	for i := uint64(0); i <= 994; i++ {
   272  		T := uint64(now - 1000 + i) // update every second for the last 1000 seconds
   273  		value, err := lookup.Lookup(T, lookup.NoClue, readFunc)
   274  		if err != nil {
   275  			t.Fatal(err)
   276  		}
   277  		data, _ := value.(*Data)
   278  		if data == nil {
   279  			t.Fatalf("Expected lookup to return %d, got nil", T)
   280  		}
   281  		if data.Payload != T {
   282  			t.Fatalf("Expected lookup to return %d, got %d", T, data.Time)
   283  		}
   284  	}
   285  }
   286  
   287  func TestSparseUpdates(t *testing.T) {
   288  
   289  	store := make(Store)
   290  	readCount := 0
   291  	readFunc := makeReadFunc(store, &readCount)
   292  
   293  	// write an update every 5 years 3 times starting in Jan 1st 1970 and then silence
   294  
   295  	now := uint64(1533799046)
   296  	var epoch lookup.Epoch
   297  
   298  	var lastData *Data
   299  	for i := uint64(0); i < 5; i++ {
   300  		T := uint64(Year * 5 * i) // write an update every 5 years 3 times starting in Jan 1st 1970 and then silence
   301  		data := Data{
   302  			Payload: T, //our "payload" will be the timestamp itself.
   303  			Time:    T,
   304  		}
   305  		epoch = update(store, epoch, T, &data)
   306  		lastData = &data
   307  	}
   308  
   309  	// try to get the last value
   310  
   311  	value, err := lookup.Lookup(now, lookup.NoClue, readFunc)
   312  	if err != nil {
   313  		t.Fatal(err)
   314  	}
   315  
   316  	readCountWithoutHint := readCount
   317  
   318  	if value != lastData {
   319  		t.Fatalf("Expected lookup to return the last written value: %v. Got %v", lastData, value)
   320  	}
   321  
   322  	// reset the read count for the next test
   323  	readCount = 0
   324  	// Provide a hint to get a faster lookup. In particular, we give the exact location of the last update
   325  	value, err = lookup.Lookup(now, epoch, readFunc)
   326  	if err != nil {
   327  		t.Fatal(err)
   328  	}
   329  
   330  	if value != lastData {
   331  		t.Fatalf("Expected lookup to return the last written value: %v. Got %v", lastData, value)
   332  	}
   333  
   334  	if readCount > readCountWithoutHint {
   335  		t.Fatalf("Expected lookup to complete with fewer reads than %d since we provided a hint. Did %d reads.", readCountWithoutHint, readCount)
   336  	}
   337  
   338  }
   339  
   340  // testG will hold precooked test results
   341  // fields are abbreviated to reduce the size of the literal below
   342  type testG struct {
   343  	e lookup.Epoch // last
   344  	n uint64       // next level
   345  	x uint8        // expected result
   346  }
   347  
   348  // test cases
   349  var testGetNextLevelCases []testG = []testG{{e: lookup.Epoch{Time: 989875233, Level: 12}, n: 989875233, x: 11}, {e: lookup.Epoch{Time: 995807650, Level: 18}, n: 995598156, x: 19}, {e: lookup.Epoch{Time: 969167082, Level: 0}, n: 968990357, x: 18}, {e: lookup.Epoch{Time: 993087628, Level: 14}, n: 992987044, x: 20}, {e: lookup.Epoch{Time: 963364631, Level: 20}, n: 963364630, x: 19}, {e: lookup.Epoch{Time: 963497510, Level: 16}, n: 963370732, x: 18}, {e: lookup.Epoch{Time: 955421349, Level: 22}, n: 955421348, x: 21}, {e: lookup.Epoch{Time: 968220379, Level: 15}, n: 968220378, x: 14}, {e: lookup.Epoch{Time: 939129014, Level: 6}, n: 939128771, x: 11}, {e: lookup.Epoch{Time: 907847903, Level: 6}, n: 907791833, x: 18}, {e: lookup.Epoch{Time: 910835564, Level: 15}, n: 910835564, x: 14}, {e: lookup.Epoch{Time: 913578333, Level: 22}, n: 881808431, x: 25}, {e: lookup.Epoch{Time: 895818460, Level: 3}, n: 895818132, x: 9}, {e: lookup.Epoch{Time: 903843025, Level: 24}, n: 895609561, x: 23}, {e: lookup.Epoch{Time: 877889433, Level: 13}, n: 877877093, x: 15}, {e: lookup.Epoch{Time: 901450396, Level: 10}, n: 901450058, x: 9}, {e: lookup.Epoch{Time: 925179910, Level: 3}, n: 925168393, x: 16}, {e: lookup.Epoch{Time: 913485477, Level: 21}, n: 913485476, x: 20}, {e: lookup.Epoch{Time: 924462991, Level: 18}, n: 924462990, x: 17}, {e: lookup.Epoch{Time: 941175128, Level: 13}, n: 941175127, x: 12}, {e: lookup.Epoch{Time: 920126583, Level: 3}, n: 920100782, x: 19}, {e: lookup.Epoch{Time: 932403200, Level: 9}, n: 932279891, x: 17}, {e: lookup.Epoch{Time: 948284931, Level: 2}, n: 948284921, x: 9}, {e: lookup.Epoch{Time: 953540997, Level: 7}, n: 950547986, x: 22}, {e: lookup.Epoch{Time: 926639837, Level: 18}, n: 918608882, x: 24}, {e: lookup.Epoch{Time: 954637598, Level: 1}, n: 954578761, x: 17}, {e: lookup.Epoch{Time: 943482981, Level: 10}, n: 942924151, x: 19}, {e: lookup.Epoch{Time: 963580771, Level: 7}, n: 963580771, x: 6}, {e: lookup.Epoch{Time: 993744930, Level: 7}, n: 993690858, x: 16}, {e: lookup.Epoch{Time: 1018890213, Level: 12}, n: 1018890212, x: 11}, {e: lookup.Epoch{Time: 1030309411, Level: 2}, n: 1030309227, x: 9}, {e: lookup.Epoch{Time: 1063204997, Level: 20}, n: 1063204996, x: 19}, {e: lookup.Epoch{Time: 1094340832, Level: 6}, n: 1094340633, x: 7}, {e: lookup.Epoch{Time: 1077880597, Level: 10}, n: 1075914292, x: 20}, {e: lookup.Epoch{Time: 1051114957, Level: 18}, n: 1051114957, x: 17}, {e: lookup.Epoch{Time: 1045649701, Level: 22}, n: 1045649700, x: 21}, {e: lookup.Epoch{Time: 1066198885, Level: 14}, n: 1066198884, x: 13}, {e: lookup.Epoch{Time: 1053231952, Level: 1}, n: 1053210845, x: 16}, {e: lookup.Epoch{Time: 1068763404, Level: 14}, n: 1068675428, x: 18}, {e: lookup.Epoch{Time: 1039042173, Level: 15}, n: 1038973110, x: 17}, {e: lookup.Epoch{Time: 1050747636, Level: 6}, n: 1050747364, x: 9}, {e: lookup.Epoch{Time: 1030034434, Level: 23}, n: 1030034433, x: 22}, {e: lookup.Epoch{Time: 1003783425, Level: 18}, n: 1003783424, x: 17}, {e: lookup.Epoch{Time: 988163976, Level: 15}, n: 988084064, x: 17}, {e: lookup.Epoch{Time: 1007222377, Level: 15}, n: 1007222377, x: 14}, {e: lookup.Epoch{Time: 1001211375, Level: 13}, n: 1001208178, x: 14}, {e: lookup.Epoch{Time: 997623199, Level: 8}, n: 997623198, x: 7}, {e: lookup.Epoch{Time: 1026283830, Level: 10}, n: 1006681704, x: 24}, {e: lookup.Epoch{Time: 1019421907, Level: 20}, n: 1019421906, x: 19}, {e: lookup.Epoch{Time: 1043154306, Level: 16}, n: 1043108343, x: 16}, {e: lookup.Epoch{Time: 1075643767, Level: 17}, n: 1075325898, x: 18}, {e: lookup.Epoch{Time: 1043726309, Level: 20}, n: 1043726308, x: 19}, {e: lookup.Epoch{Time: 1056415324, Level: 17}, n: 1056415324, x: 16}, {e: lookup.Epoch{Time: 1088650219, Level: 13}, n: 1088650218, x: 12}, {e: lookup.Epoch{Time: 1088551662, Level: 7}, n: 1088543355, x: 13}, {e: lookup.Epoch{Time: 1069667265, Level: 6}, n: 1069667075, x: 7}, {e: lookup.Epoch{Time: 1079145970, Level: 18}, n: 1079145969, x: 17}, {e: lookup.Epoch{Time: 1083338876, Level: 7}, n: 1083338875, x: 6}, {e: lookup.Epoch{Time: 1051581086, Level: 4}, n: 1051568869, x: 14}, {e: lookup.Epoch{Time: 1028430882, Level: 4}, n: 1028430864, x: 5}, {e: lookup.Epoch{Time: 1057356462, Level: 1}, n: 1057356417, x: 5}, {e: lookup.Epoch{Time: 1033104266, Level: 0}, n: 1033097479, x: 13}, {e: lookup.Epoch{Time: 1031391367, Level: 11}, n: 1031387304, x: 14}, {e: lookup.Epoch{Time: 1049781164, Level: 15}, n: 1049781163, x: 14}, {e: lookup.Epoch{Time: 1027271628, Level: 12}, n: 1027271627, x: 11}, {e: lookup.Epoch{Time: 1057270560, Level: 23}, n: 1057270560, x: 22}, {e: lookup.Epoch{Time: 1047501317, Level: 15}, n: 1047501317, x: 14}, {e: lookup.Epoch{Time: 1058349035, Level: 11}, n: 1045175573, x: 24}, {e: lookup.Epoch{Time: 1057396147, Level: 20}, n: 1057396147, x: 19}, {e: lookup.Epoch{Time: 1048906375, Level: 18}, n: 1039616919, x: 25}, {e: lookup.Epoch{Time: 1074294831, Level: 20}, n: 1074294831, x: 19}, {e: lookup.Epoch{Time: 1088946052, Level: 1}, n: 1088917364, x: 14}, {e: lookup.Epoch{Time: 1112337595, Level: 17}, n: 1111008110, x: 22}, {e: lookup.Epoch{Time: 1099990284, Level: 5}, n: 1099968370, x: 15}, {e: lookup.Epoch{Time: 1087036441, Level: 16}, n: 1053967855, x: 25}, {e: lookup.Epoch{Time: 1069225185, Level: 8}, n: 1069224660, x: 10}, {e: lookup.Epoch{Time: 1057505479, Level: 9}, n: 1057505170, x: 14}, {e: lookup.Epoch{Time: 1072381377, Level: 12}, n: 1065950959, x: 22}, {e: lookup.Epoch{Time: 1093887139, Level: 8}, n: 1093863305, x: 14}, {e: lookup.Epoch{Time: 1082366510, Level: 24}, n: 1082366510, x: 23}, {e: lookup.Epoch{Time: 1103231132, Level: 14}, n: 1102292201, x: 22}, {e: lookup.Epoch{Time: 1094502355, Level: 3}, n: 1094324652, x: 18}, {e: lookup.Epoch{Time: 1068488344, Level: 12}, n: 1067577330, x: 19}, {e: lookup.Epoch{Time: 1050278233, Level: 12}, n: 1050278232, x: 11}, {e: lookup.Epoch{Time: 1047660768, Level: 5}, n: 1047652137, x: 17}, {e: lookup.Epoch{Time: 1060116167, Level: 11}, n: 1060114091, x: 12}, {e: lookup.Epoch{Time: 1068149392, Level: 21}, n: 1052074801, x: 24}, {e: lookup.Epoch{Time: 1081934120, Level: 6}, n: 1081933847, x: 8}, {e: lookup.Epoch{Time: 1107943693, Level: 16}, n: 1107096139, x: 25}, {e: lookup.Epoch{Time: 1131571649, Level: 9}, n: 1131570428, x: 11}, {e: lookup.Epoch{Time: 1123139367, Level: 0}, n: 1122912198, x: 20}, {e: lookup.Epoch{Time: 1121144423, Level: 6}, n: 1120568289, x: 20}, {e: lookup.Epoch{Time: 1089932411, Level: 17}, n: 1089932410, x: 16}, {e: lookup.Epoch{Time: 1104899012, Level: 22}, n: 1098978789, x: 22}, {e: lookup.Epoch{Time: 1094588059, Level: 21}, n: 1094588059, x: 20}, {e: lookup.Epoch{Time: 1114987438, Level: 24}, n: 1114987437, x: 23}, {e: lookup.Epoch{Time: 1084186305, Level: 7}, n: 1084186241, x: 6}, {e: lookup.Epoch{Time: 1058827111, Level: 8}, n: 1058826504, x: 9}, {e: lookup.Epoch{Time: 1090679810, Level: 12}, n: 1090616539, x: 17}, {e: lookup.Epoch{Time: 1084299475, Level: 23}, n: 1084299475, x: 22}}
   350  
   351  func TestGetNextLevel(t *testing.T) {
   352  
   353  	// First, test well-known cases
   354  	last := lookup.Epoch{
   355  		Time:  1533799046,
   356  		Level: 5,
   357  	}
   358  
   359  	level := lookup.GetNextLevel(last, last.Time)
   360  	expected := uint8(4)
   361  	if level != expected {
   362  		t.Fatalf("Expected GetNextLevel to return %d for same-time updates at a nonzero level, got %d", expected, level)
   363  	}
   364  
   365  	level = lookup.GetNextLevel(last, last.Time+(1<<lookup.HighestLevel)+3000)
   366  	expected = lookup.HighestLevel
   367  	if level != expected {
   368  		t.Fatalf("Expected GetNextLevel to return %d for updates set 2^lookup.HighestLevel seconds away, got %d", expected, level)
   369  	}
   370  
   371  	level = lookup.GetNextLevel(last, last.Time+(1<<last.Level))
   372  	expected = last.Level
   373  	if level != expected {
   374  		t.Fatalf("Expected GetNextLevel to return %d for updates set 2^last.Level seconds away, got %d", expected, level)
   375  	}
   376  
   377  	last.Level = 0
   378  	level = lookup.GetNextLevel(last, last.Time)
   379  	expected = 0
   380  	if level != expected {
   381  		t.Fatalf("Expected GetNextLevel to return %d for same-time updates at a zero level, got %d", expected, level)
   382  	}
   383  
   384  	// run a batch of 100 cooked tests
   385  	for _, s := range testGetNextLevelCases {
   386  		level := lookup.GetNextLevel(s.e, s.n)
   387  		if level != s.x {
   388  			t.Fatalf("Expected GetNextLevel to return %d for last=%s when now=%d, got %d", s.x, s.e.String(), s.n, level)
   389  		}
   390  	}
   391  
   392  }
   393  
   394  // cookGetNextLevelTests is used to generate a deterministic
   395  // set of cases for TestGetNextLevel and thus "freeze" its current behavior
   396  func CookGetNextLevelTests(t *testing.T) {
   397  	st := ""
   398  	var last lookup.Epoch
   399  	last.Time = 1000000000
   400  	var now uint64
   401  	var expected uint8
   402  	for i := 0; i < 100; i++ {
   403  		last.Time += uint64(rand.Intn(1<<26)) - (1 << 25)
   404  		last.Level = uint8(rand.Intn(25))
   405  		v := last.Level + uint8(rand.Intn(lookup.HighestLevel))
   406  		if v > lookup.HighestLevel {
   407  			v = 0
   408  		}
   409  		now = last.Time + uint64(rand.Intn(1<<v+1)) - (1 << v)
   410  		expected = lookup.GetNextLevel(last, now)
   411  		st = fmt.Sprintf("%s,testG{e:lookup.Epoch{Time:%d, Level:%d}, n:%d, x:%d}", st, last.Time, last.Level, now, expected)
   412  	}
   413  	fmt.Println(st)
   414  }