diff --git a/cmd/lsif-test/args.go b/cmd/lsif-test/args.go
new file mode 100644
index 0000000..958ebaf
--- /dev/null
+++ b/cmd/lsif-test/args.go
@@ -0,0 +1,34 @@
+package main
+
+import (
+	"os"
+
+	"github.com/alecthomas/kingpin"
+)
+
+var app = kingpin.New(
+	"lsif-test",
+	"lsif-test is test runner for validating LSIF indexer output.",
+).Version(version)
+
+var (
+	indexFile *os.File
+	testsFile *os.File
+)
+
+func init() {
+	app.HelpFlag.Short('h')
+	app.VersionFlag.Short('v')
+	app.HelpFlag.Hidden()
+
+	app.Arg("index-file", "The LSIF index to visualize.").Default("dump.lsif").FileVar(&indexFile)
+	app.Arg("tests-file", "The test specification file.").Default("tests.yaml").FileVar(&testsFile)
+}
+
+func parseArgs(args []string) (err error) {
+	if _, err := app.Parse(args); err != nil {
+		return err
+	}
+
+	return nil
+}
diff --git a/cmd/lsif-test/internal/runner/context.go b/cmd/lsif-test/internal/runner/context.go
new file mode 100644
index 0000000..8b2c95b
--- /dev/null
+++ b/cmd/lsif-test/internal/runner/context.go
@@ -0,0 +1,15 @@
+package runner
+
+import (
+	"github.com/sourcegraph/lsif-test/internal/reader"
+)
+
+type RunnerContext struct {
+	Stasher *reader.Stasher
+}
+
+func NewRunnerContext() *RunnerContext {
+	return &RunnerContext{
+		Stasher: reader.NewStasher(),
+	}
+}
diff --git a/cmd/lsif-test/internal/runner/runner.go b/cmd/lsif-test/internal/runner/runner.go
new file mode 100644
index 0000000..6132090
--- /dev/null
+++ b/cmd/lsif-test/internal/runner/runner.go
@@ -0,0 +1,57 @@
+package runner
+
+import (
+	"fmt"
+	"io"
+	"os"
+
+	reader "github.com/sourcegraph/lsif-protocol/reader"
+	"github.com/sourcegraph/lsif-test/cmd/lsif-test/internal/search"
+	reader2 "github.com/sourcegraph/lsif-test/internal/reader"
+)
+
+type Runner struct {
+	Context *RunnerContext
+}
+
+func (v *Runner) Run(indexFile, testsFile io.Reader) error {
+	testSpecs, err := ReadTestSpecs(testsFile)
+	if err != nil {
+		return err
+	}
+
+	if err := reader2.Read(indexFile, v.Context.Stasher, nil, nil); err != nil {
+		return err
+	}
+
+	var vertices []reader.Element
+	_ = v.Context.Stasher.Vertices(func(lineContext reader2.LineContext) bool {
+		vertices = append(vertices, lineContext.Element)
+		return true
+	})
+
+	var edges []reader.Element
+	_ = v.Context.Stasher.Edges(func(lineContext reader2.LineContext, edge reader.Edge) bool {
+		edges = append(edges, lineContext.Element)
+		return true
+	})
+
+	for _, testSpec := range testSpecs {
+		rangeData := search.GatherRangeDataFromPosition(vertices, edges, testSpec.Path, testSpec.Line, testSpec.Character)
+		if len(rangeData) != 1 {
+			fmt.Printf("error: no or overlapping range data\n")
+			os.Exit(1)
+		}
+
+		if rangeData[0].HoverText != testSpec.HoverText {
+			fmt.Printf("error: bad hover text\n")
+			os.Exit(1)
+		}
+
+		// TODO - test definitions
+		// TODO - test references
+		// TODO - test monikers
+	}
+
+	return nil
+}
diff --git a/cmd/lsif-test/internal/runner/spec.go b/cmd/lsif-test/internal/runner/spec.go
new file mode 100644
index 0000000..4abdd2d
--- /dev/null
+++ b/cmd/lsif-test/internal/runner/spec.go
@@ -0,0 +1,39 @@
+package runner
+
+import (
+	"io"
+	"io/ioutil"
+
+	"gopkg.in/yaml.v2"
+)
+
+type TestSpec struct {
+	Path        string     `yaml:"path"`
+	Line        int        `yaml:"line"`
+	Character   int        `yaml:"character"`
+	HoverText   string     `yaml:"hoverText"`
+	Definitions []Location `yaml:"definitions"`
+	References  []Location `yaml:"references"`
+}
+
+type Location struct {
+	Path           string `yaml:"path"`
+	StartLine      int    `yaml:"startLine"`
+	StartCharacter int    `yaml:"startCharacter"`
+	EndLine        int    `yaml:"endLine"`
+	EndCharacter   int    `yaml:"endCharacter"`
+}
+
+func ReadTestSpecs(r io.Reader) ([]TestSpec, error) {
+	content, err := ioutil.ReadAll(r)
+	if err != nil {
+		return nil, err
+	}
+
+	var testSpecs []TestSpec
+	if err := yaml.Unmarshal(content, &testSpecs); err != nil {
+		return nil, err
+	}
+
+	return testSpecs, nil
+}
diff --git a/cmd/lsif-test/internal/search/search.go b/cmd/lsif-test/internal/search/search.go
new file mode 100644
index 0000000..77de59f
--- /dev/null
+++ b/cmd/lsif-test/internal/search/search.go
@@ -0,0 +1,241 @@
+package search
+
+import (
+	"strings"
+
+	"github.com/sourcegraph/lsif-protocol/reader"
+)
+
+type RangeData struct {
+	HoverText   string
+	Definitions []Location
+	References  []Location
+}
+
+type Location struct {
+	Path           string
+	StartLine      int
+	StartCharacter int
+	EndLine        int
+	EndCharacter   int
+}
+
+func GatherRangeDataFromPosition(vertices, edges []reader.Element, path string, line, character int) []RangeData {
+	var rangeData []RangeData
+	for _, rangeID := range findRangeByPosition(vertices, edges, path, line, character) {
+		rangeData = append(rangeData, gatherRangeDataFromID(vertices, edges, rangeID))
+	}
+
+	return rangeData
+}
+
+func gatherRangeDataFromID(vertices, edges []reader.Element, rangeID int) RangeData {
+	return RangeData{
+		HoverText:   findHoverTextByRangeID(vertices, edges, rangeID),
+		Definitions: findDefinitionLocationsByRangeID(vertices, edges, rangeID),
+		References:  findReferenceLocationsByRangeID(vertices, edges, rangeID),
+	}
+}
+
+func findRangeByPosition(vertices, edges []reader.Element, path string, line, character int) []int {
+	projectRoot := getProjectRoot(vertices, edges)
+
+	for _, vertex := range vertices {
+		if vertex.Label == "document" && strings.TrimPrefix(vertex.Payload.(string), projectRoot) == path {
+			return findOverlappingRanges(vertices, edges, findRangesContainedByDocument(vertices, edges, vertex.ID), line, character)
+		}
+	}
+
+	return nil
+}
+
+func getProjectRoot(vertices, edges []reader.Element) string {
+	for _, vertex := range vertices {
+		if vertex.Label == "metaData" {
+			projectRoot := vertex.Payload.(reader.MetaData).ProjectRoot
+			if !strings.HasSuffix(projectRoot, "/") {
+				projectRoot += "/"
+			}
+
+			return projectRoot
+		}
+	}
+
+	return ""
+}
+
+func findRangesContainedByDocument(vertices, edges []reader.Element, documentID int) []int {
+	for _, edge := range edges {
+		if payload := edge.Payload.(reader.Edge); edge.Label == "contains" && payload.OutV == documentID {
+			return payload.InVs
+		}
+	}
+
+	return nil
+}
+
+func findOverlappingRanges(vertices, edges []reader.Element, rangeIDs []int, line, character int) []int {
+	rangeIDMap := map[int]struct{}{}
+	for _, rangeID := range rangeIDs {
+		rangeIDMap[rangeID] = struct{}{}
+	}
+
+	var intersectingRangeIDs []int
+	for _, vertex := range vertices {
+		if _, ok := rangeIDMap[vertex.ID]; ok && contains(vertex.Payload.(reader.Range), line, character) {
+			intersectingRangeIDs = append(intersectingRangeIDs, vertex.ID)
+		}
+	}
+
+	return intersectingRangeIDs
+}
+
+func contains(r reader.Range, line, character int) bool {
+	if r.StartLine > line || r.EndLine < line {
+		return false
+	}
+	if r.StartLine == line && r.StartCharacter > character {
+		return false
+	}
+	if r.EndLine == line && r.EndCharacter < character {
+		return false
+	}
+
+	return true
+}
+
+func findHoverTextByRangeID(vertices, edges []reader.Element, rangeID int) string {
+	for _, edge := range edges {
+		if payload := edge.Payload.(reader.Edge); edge.Label == "textDocument/hover" && payload.OutV == rangeID {
+			return findHoverTextByID(vertices, edges, payload.InV)
+		}
+	}
+
+	for _, edge := range edges {
+		if payload := edge.Payload.(reader.Edge); edge.Label == "next" && payload.OutV == rangeID {
+			if hoverText := findHoverTextByRangeID(vertices, edges, payload.InV); hoverText != "" {
+				return hoverText
+			}
+		}
+	}
+
+	return ""
+}
+
+func findHoverTextByID(vertices, edges []reader.Element, hoverResultID int) string {
+	for _, vertex := range vertices {
+		if vertex.Label == "hoverResult" && vertex.ID == hoverResultID {
+			return vertex.Payload.(string)
+		}
+	}
+
+	return ""
+}
+
+//
+//
+// TODO
+//
+//
+
+func findDefinitionLocationsByRangeID(vertices, edges []reader.Element, rangeID int) []Location {
+	for _, edge := range edges {
+		if payload := edge.Payload.(reader.Edge); edge.Label == "textDocument/definition" && payload.OutV == rangeID {
+			return findDefinitionLocationsByID(vertices, edges, payload.InV)
+		}
+	}
+
+	for _, edge := range edges {
+		if payload := edge.Payload.(reader.Edge); edge.Label == "next" && payload.OutV == rangeID {
+			if locations := findDefinitionLocationsByRangeID(vertices, edges, payload.InV); len(locations) > 0 {
+				return locations
+			}
+		}
+	}
+
+	return nil
+}
+
+func findDefinitionLocationsByID(vertices, edges []reader.Element, definitionResultID int) []Location {
+	var locations []Location
+	for _, edge := range edges {
+		if payload := edge.Payload.(reader.Edge); edge.Label == "item" && payload.OutV == definitionResultID {
+			for _, inV := range payload.InVs {
+				locations = append(locations, findLocationByID(vertices, edges, inV))
+			}
+		}
+	}
+
+	return locations
+}
+
+func findReferenceLocationsByRangeID(vertices, edges []reader.Element, rangeID int) []Location {
+	for _, edge := range edges {
+		if payload := edge.Payload.(reader.Edge); edge.Label == "textDocument/references" && payload.OutV == rangeID {
+			return findReferenceLocationsByID(vertices, edges, payload.InV)
+		}
+	}
+
+	for _, edge := range edges {
+		if payload := edge.Payload.(reader.Edge); edge.Label == "next" && payload.OutV == rangeID {
+			if locations := findReferenceLocationsByRangeID(vertices, edges, payload.InV); len(locations) > 0 {
+				return locations
+			}
+		}
+	}
+
+	return nil
+}
+
+func findReferenceLocationsByID(vertices, edges []reader.Element, referenceResultID int) []Location {
+	var locations []Location
+	for _, edge := range edges {
+		if payload := edge.Payload.(reader.Edge); edge.Label == "item" && payload.OutV == referenceResultID {
+			for _, inV := range payload.InVs {
+				locations = append(locations, findLocationByID(vertices, edges, inV))
+			}
+		}
+	}
+
+	return locations
+}
+
+func findLocationByID(vertices, edges []reader.Element, rangeID int) Location {
+	for _, vertex := range vertices {
+		if vertex.Label == "range" && vertex.ID == rangeID {
+			r := vertex.Payload.(reader.Range)
+
+			return Location{
+				Path:           findURIContaining(vertices, edges, rangeID),
+				StartLine:      r.StartLine,
+				StartCharacter: r.StartCharacter,
+				EndLine:        r.EndLine,
+				EndCharacter:   r.EndCharacter,
+			}
+		}
+	}
+
+	return Location{}
+}
+
+func findURIContaining(vertices, edges []reader.Element, rangeID int) string {
+	for _, edge := range edges {
+		if payload := edge.Payload.(reader.Edge); edge.Label == "contains" {
+			for _, inV := range payload.InVs {
+				if inV == rangeID {
+					projectRoot := getProjectRoot(vertices, edges)
+
+					for _, vertex := range vertices {
+						if vertex.Label == "document" && vertex.ID == payload.OutV {
+							return strings.TrimPrefix(vertex.Payload.(string), projectRoot)
+						}
+					}
+
+					return ""
+				}
+			}
+		}
+	}
+
+	return ""
+}
diff --git a/cmd/lsif-test/main.go b/cmd/lsif-test/main.go
new file mode 100644
index 0000000..c9bdb28
--- /dev/null
+++ b/cmd/lsif-test/main.go
@@ -0,0 +1,25 @@
+package main
+
+import (
+	"fmt"
+	"os"
+)
+
+const version = "0.1.0"
+
+func main() {
+	if err := mainErr(); err != nil {
+		fmt.Fprint(os.Stderr, fmt.Sprintf("\nerror: %v\n", err))
+		os.Exit(1)
+	}
+}
+
+func mainErr() error {
+	if err := parseArgs(os.Args[1:]); err != nil {
+		return err
+	}
+	defer indexFile.Close()
+	defer testsFile.Close()
+
+	return test(indexFile, testsFile)
+}
diff --git a/cmd/lsif-test/test.go b/cmd/lsif-test/test.go
new file mode 100644
index 0000000..7de2318
--- /dev/null
+++ b/cmd/lsif-test/test.go
@@ -0,0 +1,13 @@
+package main
+
+import (
+	"os"
+
+	"github.com/sourcegraph/lsif-test/cmd/lsif-test/internal/runner"
+)
+
+func test(indexFile, testsFile *os.File) error {
+	ctx := runner.NewRunnerContext()
+	runner := &runner.Runner{Context: ctx}
+	return runner.Run(indexFile, testsFile)
+}
diff --git a/cmd/lsif-test/tests.yaml b/cmd/lsif-test/tests.yaml
new file mode 100644
index 0000000..9e3a8f1
--- /dev/null
+++ b/cmd/lsif-test/tests.yaml
@@ -0,0 +1,19 @@
+- path: protocol/emitter.go
+  line: 101
+  character: 12
+  hoverText: |
+    foo
+    bar
+    baz
+    bonk
+  definitions:
+    - path: foo
+      startLine: 3
+      startCharacter: 4
+      endLine: 3
+      endCharacter: 6
+    - path: bar
+      startLine: 4
+      startCharacter: 5
+      endLine: 4
+      endCharacter: 7
diff --git a/go.mod b/go.mod
index d67bc08..50710cc 100644
--- a/go.mod
+++ b/go.mod
@@ -10,4 +10,6 @@ require (
 	github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd // indirect
 	github.com/modern-go/reflect2 v1.0.1 // indirect
 	github.com/sourcegraph/lsif-protocol v1.0.0
+	golang.org/x/tools v0.0.0-20190428024724-550556f78a90
+	gopkg.in/yaml.v2 v2.2.5
 )
diff --git a/go.sum b/go.sum
index a823ab0..f8fa536 100644
--- a/go.sum
+++ b/go.sum
@@ -50,6 +50,7 @@ golang.org/x/sys v0.0.0-20190428183149-804c0c7841b5/go.mod h1:h1NjWce9XRLGQEsW7w
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 golang.org/x/text v0.3.2/go.mod h1:bEr9sfX3Q8Zfm5fL9x+3itogRgK3+ptLWKqgva+5dAk=
 golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
+golang.org/x/tools v0.0.0-20190428024724-550556f78a90 h1:oGQGZoUHCvTWJLWXu4Qpp6uMF6gpOAGVm1hZx1KJkhU=
 golang.org/x/tools v0.0.0-20190428024724-550556f78a90/go.mod h1:RgjU9mgBXZiqYHBnxXauZ1Gv1EHHAz9KjViQ78xBX0Q=
 golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543 h1:E7g+9GITq07hpfrRu66IVDexMakfv52eLZ2CXBWiKr4=
 golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=