ValidateAvailability implementation

crypto/random.go

@@ -16,7 +16,7 @@ func randBytes(numBytes int) []byte {
 	return b
 }
 
-// This only uses the OS's randomness
+// CRandBytes returns requested number of bytes from the OS's randomness.
 func CRandBytes(numBytes int) []byte {
 	return randBytes(numBytes)
 }
@@ -29,7 +29,18 @@ func CRandHex(numDigits int) string {
 	return hex.EncodeToString(CRandBytes(numDigits / 2))
 }
 
-// Returns a crand.Reader.
+// CRandSeed returns a seed from the OS's randomness.
+func CRandSeed(length int) int64 {
+	b := randBytes(length)
+	var seed uint64
+	for i := 0; i < 8; i++ {
+		seed |= uint64(b[i])
+		seed <<= 8
+	}
+	return int64(seed)
+}
+
+// CReader returns a crand.Reader.
 func CReader() io.Reader {
 	return crand.Reader
 }

go.sum

@@ -599,13 +599,11 @@ github.com/kr/pretty v0.2.1 h1:Fmg33tUaq4/8ym9TJN1x7sLJnHVwhP33CNkpYV/7rwI=
 github.com/kr/pretty v0.2.1/go.mod h1:ipq/a2n7PKx3OHsz4KJII5eveXtPO4qwEXGdVfWzfnI=
 github.com/kr/pty v1.1.1/go.mod h1:pFQYn66WHrOpPYNljwOMqo10TkYh1fy3cYio2l3bCsQ=
 github.com/kr/pty v1.1.3/go.mod h1:pFQYn66WHrOpPYNljwOMqo10TkYh1fy3cYio2l3bCsQ=
-github.com/kr/text v0.1.0 h1:45sCR5RtlFHMR4UwH9sdQ5TC8v0qDQCHnXt+kaKSTVE=
 github.com/kr/text v0.1.0/go.mod h1:4Jbv+DJW3UT/LiOwJeYQe1efqtUx/iVham/4vfdArNI=
 github.com/kr/text v0.2.0 h1:5Nx0Ya0ZqY2ygV366QzturHI13Jq95ApcVaJBhpS+AY=
 github.com/kr/text v0.2.0/go.mod h1:eLer722TekiGuMkidMxC/pM04lWEeraHUUmBw8l2grE=
 github.com/lazyledger/go-ipfs v0.8.0-lazypatch h1:8Dkw7Or6d0BmpFYFcxwgqWZ047BPGCsWtG7v9+H0ofk=
 github.com/lazyledger/go-ipfs v0.8.0-lazypatch/go.mod h1:CE4cJkjUmwW5LwJP26KKEAZ11ZED0DxzSryfv5RMf6E=
-github.com/lazyledger/go-leopard v0.0.0-20200604113236-298f93361181 h1:mUeCGuCgjZVadW4CzA2dMBq7p2BqaoCfpnKjxMmSaSE=
 github.com/lazyledger/go-leopard v0.0.0-20200604113236-298f93361181/go.mod h1:v1o1CRihQ9i7hizx23KK4aR79lxA6VDUIzUCfDva0XQ=
 github.com/lazyledger/go-leopard v0.0.0-20200724211609-50ec4b3fab41 h1:DTQODNWI71ZtqCT3wQg+RXl4K/zpu+hu5usISUhDq/E=
 github.com/lazyledger/go-leopard v0.0.0-20200724211609-50ec4b3fab41/go.mod h1:v1o1CRihQ9i7hizx23KK4aR79lxA6VDUIzUCfDva0XQ=
@@ -615,7 +613,6 @@ github.com/lazyledger/merkletree v0.0.0-20201214195110-6901c4c3c75f h1:jbyPAH6o6
 github.com/lazyledger/merkletree v0.0.0-20201214195110-6901c4c3c75f/go.mod h1:10PA0NlnYtB8HrtwIDQAyTKWp8TEZ0zBZCGlYC/7+QE=
 github.com/lazyledger/nmt v0.3.1 h1:zP172RR33Es4dhb88GmUr9kBpAkH6Wcl7nQGJ3HQzu4=
 github.com/lazyledger/nmt v0.3.1/go.mod h1:tY7ypPX26Sbkt6F8EbPl3AT33B5N0BJe4OVPbq849YI=
-github.com/lazyledger/rsmt2d v0.1.1-0.20210327010029-ef1d6c54461e h1:3mwa4b4v9puYIFsfRN6TsXMbUagvhLtIzXWHN2GFHB4=
 github.com/lazyledger/rsmt2d v0.1.1-0.20210327010029-ef1d6c54461e/go.mod h1:ORR2U7THCNr1fpUhwYqZN7QCFJ20iR2uiIWfXKz3KJ4=
 github.com/lazyledger/rsmt2d v0.1.1-0.20210406153014-e1fd589bdb09 h1:5wpWhlalAm1vNpkR/L1BlWHyn8GT5XNieIZqTlKG9hc=
 github.com/lazyledger/rsmt2d v0.1.1-0.20210406153014-e1fd589bdb09/go.mod h1:EbB1gGbX51gBNm0hC5lMcbkgEyO3Wj2RYwba9mCUvPA=
@@ -1168,7 +1165,6 @@ github.com/soheilhy/cmux v0.1.4/go.mod h1:IM3LyeVVIOuxMH7sFAkER9+bJ4dT7Ms6E4xg4k
 github.com/sony/gobreaker v0.4.1/go.mod h1:ZKptC7FHNvhBz7dN2LGjPVBz2sZJmc0/PkyDJOjmxWY=
 github.com/sourcegraph/annotate v0.0.0-20160123013949-f4cad6c6324d/go.mod h1:UdhH50NIW0fCiwBSr0co2m7BnFLdv4fQTgdqdJTHFeE=
 github.com/sourcegraph/syntaxhighlight v0.0.0-20170531221838-bd320f5d308e/go.mod h1:HuIsMU8RRBOtsCgI77wP899iHVBQpCmg4ErYMZB+2IA=
-github.com/spacemonkeygo/errors v0.0.0-20171212215202-9064522e9fd1 h1:xHQewZjohU9/wUsyC99navCjQDNHtTgUOM/J1jAbzfw=
 github.com/spacemonkeygo/errors v0.0.0-20171212215202-9064522e9fd1/go.mod h1:7NL9UAYQnRM5iKHUCld3tf02fKb5Dft+41+VckASUy0=
 github.com/spacemonkeygo/openssl v0.0.0-20181017203307-c2dcc5cca94a/go.mod h1:7AyxJNCJ7SBZ1MfVQCWD6Uqo2oubI2Eq2y2eqf+A5r0=
 github.com/spacemonkeygo/spacelog v0.0.0-20180420211403-2296661a0572 h1:RC6RW7j+1+HkWaX/Yh71Ee5ZHaHYt7ZP4sQgUrm6cDU=
@@ -1229,7 +1225,6 @@ github.com/urfave/cli v1.22.1/go.mod h1:Gos4lmkARVdJ6EkW0WaNv/tZAAMe9V7XWyB60NtX
 github.com/urfave/cli/v2 v2.0.0/go.mod h1:SE9GqnLQmjVa0iPEY0f1w3ygNIYcIJ0OKPMoW2caLfQ=
 github.com/viant/assertly v0.4.8/go.mod h1:aGifi++jvCrUaklKEKT0BU95igDNaqkvz+49uaYMPRU=
 github.com/viant/toolbox v0.24.0/go.mod h1:OxMCG57V0PXuIP2HNQrtJf2CjqdmbrOx5EkMILuUhzM=
-github.com/vivint/infectious v0.0.0-20190108171102-2455b059135b h1:dLkqBELopfQNhe8S9ucnSf+HhiUCgK/hPIjVG0f9GlY=
 github.com/vivint/infectious v0.0.0-20190108171102-2455b059135b/go.mod h1:5oyMAv4hrBEKqBwORFsiqIrCNCmL2qcZLQTdJLYeYIc=
 github.com/vivint/infectious v0.0.0-20200605153912-25a574ae18a3 h1:zMsHhfK9+Wdl1F7sIKLyx3wrOFofpb3rWFbA4HgcK5k=
 github.com/vivint/infectious v0.0.0-20200605153912-25a574ae18a3/go.mod h1:R0Gbuw7ElaGSLOZUSwBm/GgVwMd30jWxBDdAyMOeTuc=
@@ -1267,7 +1262,6 @@ github.com/xordataexchange/crypt v0.0.3-0.20170626215501-b2862e3d0a77/go.mod h1:
 github.com/yuin/goldmark v1.1.27/go.mod h1:3hX8gzYuyVAZsxl0MRgGTJEmQBFcNTphYh9decYSb74=
 github.com/yuin/goldmark v1.1.32/go.mod h1:3hX8gzYuyVAZsxl0MRgGTJEmQBFcNTphYh9decYSb74=
 github.com/yuin/goldmark v1.2.1/go.mod h1:3hX8gzYuyVAZsxl0MRgGTJEmQBFcNTphYh9decYSb74=
-gitlab.com/NebulousLabs/errors v0.0.0-20171229012116-7ead97ef90b8 h1:gZfMjx7Jr6N8b7iJO4eUjDsn6xJqoyXg8D+ogdoAfKY=
 gitlab.com/NebulousLabs/errors v0.0.0-20171229012116-7ead97ef90b8/go.mod h1:ZkMZ0dpQyWwlENaeZVBiQRjhMEZvk6VTXquzl3FOFP8=
 gitlab.com/NebulousLabs/errors v0.0.0-20200929122200-06c536cf6975 h1:L/ENs/Ar1bFzUeKx6m3XjlmBgIUlykX9dzvp5k9NGxc=
 gitlab.com/NebulousLabs/errors v0.0.0-20200929122200-06c536cf6975/go.mod h1:ZkMZ0dpQyWwlENaeZVBiQRjhMEZvk6VTXquzl3FOFP8=
@@ -1359,6 +1353,7 @@ golang.org/x/exp v0.0.0-20191030013958-a1ab85dbe136/go.mod h1:JXzH8nQsPlswgeRAPE
 golang.org/x/exp v0.0.0-20191129062945-2f5052295587/go.mod h1:2RIsYlXP63K8oxa1u096TMicItID8zy7Y6sNkU49FU4=
 golang.org/x/exp v0.0.0-20191227195350-da58074b4299/go.mod h1:2RIsYlXP63K8oxa1u096TMicItID8zy7Y6sNkU49FU4=
 golang.org/x/exp v0.0.0-20200207192155-f17229e696bd/go.mod h1:J/WKrq2StrnmMY6+EHIKF9dgMWnmCNThgcyBT1FY9mM=
+golang.org/x/exp v0.0.0-20200331195152-e8c3332aa8e5/go.mod h1:4M0jN8W1tt0AVLNr8HDosyJCDCDuyL9N9+3m7wDWgKw=
 golang.org/x/image v0.0.0-20180708004352-c73c2afc3b81/go.mod h1:ux5Hcp/YLpHSI86hEcLt0YII63i6oz57MZXIpbrjZUs=
 golang.org/x/image v0.0.0-20190227222117-0694c2d4d067/go.mod h1:kZ7UVZpmo3dzQBMxlp+ypCbDeSB+sBbTgSJuh5dn5js=
 golang.org/x/image v0.0.0-20190802002840-cff245a6509b/go.mod h1:FeLwcggjj3mMvU+oOTbSwawSJRM1uh48EjtB4UJZlP0=
@@ -1419,7 +1414,6 @@ golang.org/x/net v0.0.0-20200520182314-0ba52f642ac2/go.mod h1:qpuaurCH72eLCgpAm/
 golang.org/x/net v0.0.0-20200625001655-4c5254603344/go.mod h1:/O7V0waA8r7cgGh81Ro3o1hOxt32SMVPicZroKQ2sZA=
 golang.org/x/net v0.0.0-20200707034311-ab3426394381/go.mod h1:/O7V0waA8r7cgGh81Ro3o1hOxt32SMVPicZroKQ2sZA=
 golang.org/x/net v0.0.0-20200813134508-3edf25e44fcc/go.mod h1:/O7V0waA8r7cgGh81Ro3o1hOxt32SMVPicZroKQ2sZA=
-golang.org/x/net v0.0.0-20201021035429-f5854403a974 h1:IX6qOQeG5uLjB/hjjwjedwfjND0hgjPMMyO1RoIXQNI=
 golang.org/x/net v0.0.0-20201021035429-f5854403a974/go.mod h1:sp8m0HH+o8qH0wwXwYZr8TS3Oi6o0r6Gce1SSxlDquU=
 golang.org/x/net v0.0.0-20210226172049-e18ecbb05110 h1:qWPm9rbaAMKs8Bq/9LRpbMqxWRVUAQwMI9fVrssnTfw=
 golang.org/x/net v0.0.0-20210226172049-e18ecbb05110/go.mod h1:m0MpNAwzfU5UDzcl9v0D8zg8gWTRqZa9RBIspLL5mdg=
@@ -1495,7 +1489,6 @@ golang.org/x/sys v0.0.0-20200615200032-f1bc736245b1/go.mod h1:h1NjWce9XRLGQEsW7w
 golang.org/x/sys v0.0.0-20200625212154-ddb9806d33ae/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20200814200057-3d37ad5750ed/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20200930185726-fdedc70b468f/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/sys v0.0.0-20201015000850-e3ed0017c211 h1:9UQO31fZ+0aKQOFldThf7BKPMJTiBfWycGh/u3UoO88=
 golang.org/x/sys v0.0.0-20201015000850-e3ed0017c211/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20201119102817-f84b799fce68/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20210403161142-5e06dd20ab57 h1:F5Gozwx4I1xtr/sr/8CFbb57iKi3297KFs0QDbGN60A=
@@ -1561,9 +1554,7 @@ golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8T
 golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1 h1:go1bK/D/BFZV2I8cIQd1NKEZ+0owSTG1fDTci4IqFcE=
 golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 gonum.org/v1/gonum v0.0.0-20180816165407-929014505bf4/go.mod h1:Y+Yx5eoAFn32cQvJDxZx5Dpnq+c3wtXuadVZAcxbbBo=
-gonum.org/v1/gonum v0.7.0 h1:Hdks0L0hgznZLG9nzXb8vZ0rRvqNvAcgAp84y7Mwkgw=
 gonum.org/v1/gonum v0.7.0/go.mod h1:L02bwd0sqlsvRv41G7wGWFCsVNZFv/k1xzGIxeANHGM=
-gonum.org/v1/netlib v0.0.0-20190313105609-8cb42192e0e0 h1:OE9mWmgKkjJyEmDAAtGMPjXu+YNeGvK9VTSHY6+Qihc=
 gonum.org/v1/netlib v0.0.0-20190313105609-8cb42192e0e0/go.mod h1:wa6Ws7BG/ESfp6dHfk7C6KdzKA7wR7u/rKwOGE66zvw=
 gonum.org/v1/plot v0.0.0-20190515093506-e2840ee46a6b/go.mod h1:Wt8AAjI+ypCyYX3nZBvf6cAIx93T+c/OS2HFAYskSZc=
 google.golang.org/api v0.0.0-20180910000450-7ca32eb868bf/go.mod h1:4mhQ8q/RsB7i+udVvVy5NUi08OU8ZlA0gRVgrF7VFY0=
@@ -1663,7 +1654,6 @@ gopkg.in/yaml.v2 v2.2.5/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
 gopkg.in/yaml.v2 v2.2.8/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
 gopkg.in/yaml.v2 v2.3.0 h1:clyUAQHOM3G0M3f5vQj7LuJrETvjVot3Z5el9nffUtU=
 gopkg.in/yaml.v2 v2.3.0/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
-gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c h1:dUUwHk2QECo/6vqA44rthZ8ie2QXMNeKRTHCNY2nXvo=
 gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
 gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b h1:h8qDotaEPuJATrMmW04NCwg7v22aHH28wwpauUhK9Oo=
 gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

p2p/ipld/read.go

@@ -10,12 +10,13 @@ import (
 	"github.com/ipfs/go-cid"
 	coreiface "github.com/ipfs/interface-go-ipfs-core"
 	"github.com/ipfs/interface-go-ipfs-core/path"
+	"github.com/lazyledger/rsmt2d"
+
 	"github.com/lazyledger/lazyledger-core/p2p/ipld/plugin/nodes"
 	"github.com/lazyledger/lazyledger-core/types"
-	"github.com/lazyledger/rsmt2d"
 )
 
-// //////////////////////////////////////
+// ///////////////////////////////////////
 //	Retrieve Block Data
 // ////////////////////////////////////
 

p2p/ipld/read_test.go

@@ -12,18 +12,19 @@ import (
 	"testing"
 	"time"
 
-	cid "github.com/ipfs/go-cid"
+	"github.com/ipfs/go-cid"
 	"github.com/ipfs/go-ipfs/core/coreapi"
-
 	coremock "github.com/ipfs/go-ipfs/core/mock"
 	format "github.com/ipfs/go-ipld-format"
-	"github.com/lazyledger/lazyledger-core/p2p/ipld/plugin/nodes"
-	"github.com/lazyledger/lazyledger-core/types"
+	iface "github.com/ipfs/interface-go-ipfs-core"
 	"github.com/lazyledger/nmt"
 	"github.com/lazyledger/nmt/namespace"
 	"github.com/lazyledger/rsmt2d"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
+
+	"github.com/lazyledger/lazyledger-core/p2p/ipld/plugin/nodes"
+	"github.com/lazyledger/lazyledger-core/types"
 )
 
 var raceDetectorActive = false
@@ -98,20 +99,12 @@ func TestGetLeafData(t *testing.T) {
 		leaves  [][]byte
 	}
 
-	// create a mock node
-	ipfsNode, err := coremock.NewMockNode()
-	if err != nil {
-		t.Error(err)
-	}
+	// create the context and batch needed for node collection from the tree
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
 
 	// issue a new API object
-	ipfsAPI, err := coreapi.NewCoreAPI(ipfsNode)
-	if err != nil {
-		t.Error(err)
-	}
-
-	// create the context and batch needed for node collection from the tree
-	ctx := context.Background()
+	ipfsAPI := mockedIpfsAPI(t)
 	batch := format.NewBatch(ctx, ipfsAPI.Dag())
 
 	// generate random data for the nmt
@@ -238,17 +231,8 @@ func TestRetrieveBlockData(t *testing.T) {
 		errStr     string
 	}
 
-	// create a mock node
-	ipfsNode, err := coremock.NewMockNode()
-	if err != nil {
-		t.Error(err)
-	}
-
 	// issue a new API object
-	ipfsAPI, err := coreapi.NewCoreAPI(ipfsNode)
-	if err != nil {
-		t.Error(err)
-	}
+	ipfsAPI := mockedIpfsAPI(t)
 
 	// the max size of messages that won't get split
 	adjustedMsgSize := types.MsgShareSize - 2
@@ -447,3 +431,18 @@ func generateRandomContiguousShares(count int) types.Txs {
 	}
 	return txs
 }
+
+func mockedIpfsAPI(t *testing.T) iface.CoreAPI {
+	ipfsNode, err := coremock.NewMockNode()
+	if err != nil {
+		t.Error(err)
+	}
+
+	// issue a new API object
+	ipfsAPI, err := coreapi.NewCoreAPI(ipfsNode)
+	if err != nil {
+		t.Error(err)
+	}
+
+	return ipfsAPI
+}

p2p/ipld/sample.go

@@ -0,0 +1,108 @@
+package ipld
+
+import (
+	crand "crypto/rand"
+	"math/big"
+
+	"github.com/ipfs/go-cid"
+	"github.com/lazyledger/nmt/namespace"
+
+	"github.com/lazyledger/lazyledger-core/p2p/ipld/plugin/nodes"
+	"github.com/lazyledger/lazyledger-core/types"
+)
+
+// Sample is a point in 2D space over square.
+type Sample struct {
+	Row, Col uint32
+
+	// src defines the source for sampling, either from column(true) or row(false) root
+	src bool
+}
+
+// SampleSquare randomly picks *num* unique points from arbitrary *width* square
+// and returns them as samples.
+func SampleSquare(squareWidth uint32, num int) []Sample {
+	ss := newSquareSampler(squareWidth, num)
+	ss.sample(num)
+	return ss.samples()
+}
+
+// Leaf returns leaf info needed for retrieval using data provided with DAHeader.
+func (s Sample) Leaf(dah *types.DataAvailabilityHeader) (cid.Cid, uint32, error) {
+	var (
+		leaf uint32
+		root namespace.IntervalDigest
+	)
+
+	// spread leaves retrieval from both Row and Column roots
+	if s.src {
+		root = dah.ColumnRoots[s.Col]
+		leaf = s.Row
+	} else {
+		root = dah.RowsRoots[s.Row]
+		leaf = s.Col
+	}
+
+	rootCid, err := nodes.CidFromNamespacedSha256(root.Bytes())
+	if err != nil {
+		return cid.Undef, 0, err
+	}
+
+	return rootCid, leaf, nil
+}
+
+// Equals check whenever to samples are equal.
+func (s Sample) Equals(to Sample) bool {
+	return s.Row == to.Row && s.Col == to.Col
+}
+
+type squareSampler struct {
+	squareWidth uint32
+	smpls       map[Sample]struct{}
+}
+
+func newSquareSampler(squareWidth uint32, expectedSamples int) *squareSampler {
+	return &squareSampler{
+		squareWidth: squareWidth,
+		smpls:       make(map[Sample]struct{}, expectedSamples),
+	}
+}
+
+func (ss *squareSampler) sample(num int) {
+	if uint32(num) > ss.squareWidth*ss.squareWidth {
+		panic("number of samples must be less than square width")
+	}
+
+	done := 0
+	for done < num {
+		s := Sample{
+			Row: randUint32(ss.squareWidth),
+			Col: randUint32(ss.squareWidth),
+			src: randUint32(2) == 0,
+		}
+
+		if _, ok := ss.smpls[s]; ok {
+			continue
+		}
+
+		done++
+		ss.smpls[s] = struct{}{}
+	}
+}
+
+func (ss *squareSampler) samples() []Sample {
+	samples := make([]Sample, 0, len(ss.smpls))
+	for s := range ss.smpls {
+		samples = append(samples, s)
+	}
+	return samples
+}
+
+func randUint32(max uint32) uint32 {
+	n, err := crand.Int(crand.Reader, big.NewInt(int64(max)))
+	if err != nil {
+		panic(err) // won't panic as rand.Reader is endless
+	}
+
+	return uint32(n.Int64())
+}

p2p/ipld/sample_test.go

@@ -0,0 +1,35 @@
+package ipld
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestSampleSquare(t *testing.T) {
+	tests := []struct {
+		width   uint32
+		samples int
+	}{
+		{width: 10, samples: 5},
+		{width: 500, samples: 90},
+	}
+
+	for _, tt := range tests {
+		ss := SampleSquare(tt.width, tt.samples)
+		assert.Len(t, ss, tt.samples)
+		// check points are within width
+		for _, s := range ss {
+			assert.Less(t, s.Row, tt.width)
+			assert.Less(t, s.Col, tt.width)
+		}
+		// checks samples are not equal
+		for i, s1 := range ss {
+			for j, s2 := range ss {
+				if i != j {
+					assert.False(t, s1.Equals(s2))
+				}
+			}
+		}
+	}
+}