diff --git a/goprocess/gp.go b/goprocess/gp.go
index 87d9959c..8a53d945 100644
--- a/goprocess/gp.go
+++ b/goprocess/gp.go
@@ -32,7 +32,13 @@ func FindAll() []P {
 	if err != nil {
 		return nil
 	}
+	return findAll(pss, isGo, concurrencyLimit)
+}
+
+// Allows to inject isGo for testing.
+type isGoFunc func(ps.Process) (path, version string, agent, ok bool, err error)
 
+func findAll(pss []ps.Process, isGo isGoFunc, concurrencyLimit int) []P {
 	input := make(chan ps.Process, len(pss))
 	output := make(chan P, len(pss))
 
diff --git a/goprocess/gp_test.go b/goprocess/gp_test.go
index 7fb1b157..dd48e5e2 100644
--- a/goprocess/gp_test.go
+++ b/goprocess/gp_test.go
@@ -1,9 +1,92 @@
 package goprocess
 
-import "testing"
+import (
+	"reflect"
+	"sort"
+	"testing"
+
+	"github.com/keybase/go-ps"
+)
 
 func BenchmarkFindAll(b *testing.B) {
 	for ii := 0; ii < b.N; ii++ {
 		_ = FindAll()
 	}
 }
+
+// TestFindAll tests findAll implementation function.
+func TestFindAll(t *testing.T) {
+	for _, tc := range []struct {
+		name             string
+		concurrencyLimit int
+		input            []ps.Process
+		goPIDs           []int
+		want             []P
+	}{{
+		name:             "no processes",
+		concurrencyLimit: 10,
+		input:            nil,
+		want:             nil,
+	}, {
+		name:             "non-Go process",
+		concurrencyLimit: 10,
+		input:            fakeProcessesWithPIDs(1),
+		want:             nil,
+	}, {
+		name:             "Go process",
+		concurrencyLimit: 10,
+		input:            fakeProcessesWithPIDs(1),
+		goPIDs:           []int{1},
+		want:             []P{{PID: 1}},
+	}, {
+		name:             "filters Go processes",
+		concurrencyLimit: 10,
+		input:            fakeProcessesWithPIDs(1, 2, 3, 4, 5, 6, 7),
+		goPIDs:           []int{1, 3, 5, 7},
+		want:             []P{{PID: 1}, {PID: 3}, {PID: 5}, {PID: 7}},
+	}, {
+		name:             "Go processes above max concurrency (issue #123)",
+		concurrencyLimit: 2,
+		input:            fakeProcessesWithPIDs(1, 2, 3, 4, 5, 6, 7),
+		goPIDs:           []int{1, 3, 5, 7},
+		want:             []P{{PID: 1}, {PID: 3}, {PID: 5}, {PID: 7}},
+	}} {
+		t.Run(tc.name, func(t *testing.T) {
+			actual := findAll(tc.input, fakeIsGo(tc.goPIDs), tc.concurrencyLimit)
+			sort.Slice(actual, func(i, j int) bool { return actual[i].PID < actual[j].PID })
+			if !reflect.DeepEqual(actual, tc.want) {
+				t.Errorf("findAll(concurrency=%v)\ngot  %v\nwant %v",
+					tc.concurrencyLimit, actual, tc.want)
+			}
+		})
+	}
+}
+
+func fakeIsGo(goPIDs []int) isGoFunc {
+	return func(pr ps.Process) (path, version string, agent, ok bool, err error) {
+		for _, p := range goPIDs {
+			if p == pr.Pid() {
+				ok = true
+				return
+			}
+		}
+		return
+	}
+}
+
+func fakeProcessesWithPIDs(pids ...int) []ps.Process {
+	p := make([]ps.Process, 0, len(pids))
+	for _, pid := range pids {
+		p = append(p, fakeProcess{pid: pid})
+	}
+	return p
+}
+
+type fakeProcess struct {
+	ps.Process
+	pid int
+}
+
+func (p fakeProcess) Pid() int           { return p.pid }
+func (p fakeProcess) PPid() int          { return 0 }
+func (p fakeProcess) Executable() string { return "" }