diff --git a/docs/validation/matrix.yaml b/docs/validation/matrix.yaml
index 03a7bade..2a36f78b 100644
--- a/docs/validation/matrix.yaml
+++ b/docs/validation/matrix.yaml
@@ -35,7 +35,8 @@
 - entrypoint: bbi nonmem probs
   code: cmd/project.go
   doc: docs/commands/bbi_nonmem_probs.md
-  tests: []
+  tests:
+    - integration/nmless/bbi_probs_test.go
 
 - entrypoint: bbi nonmem reclean
   code: cmd/reclean.go
diff --git a/integration/nmless/bbi_probs_test.go b/integration/nmless/bbi_probs_test.go
new file mode 100644
index 00000000..032ec696
--- /dev/null
+++ b/integration/nmless/bbi_probs_test.go
@@ -0,0 +1,139 @@
+package nmless
+
+import (
+	"bytes"
+	"encoding/json"
+	"errors"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"testing"
+
+	"github.com/metrumresearchgroup/wrapt"
+
+	parser "github.com/metrumresearchgroup/bbi/parsers/nmparser"
+)
+
+type jsonResult struct {
+	RunName string
+	Ok      bool
+	Summary parser.ModelInfo
+}
+
+func setupMods(t *wrapt.T) string {
+	t.Helper()
+	dir := t.TempDir()
+
+	fooMod := []byte(`
+$PROB foo prob
+$SUBROUTINES ADVAN2 TRANS2x
+$EST METHOD=1 INTERACTION MAXEVAL=9999
+$EST METHOD=SAEM NBURN=3000 NITER=2000
+$TABLE ID TIME
+$TABLE ID CL
+$COV PRINT = E UNCONDITIONAL
+`)
+	err := os.WriteFile(filepath.Join(dir, "foo.mod"), fooMod, 0o666)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Same but with ctl extension.
+	err = os.WriteFile(filepath.Join(dir, "foo.ctl"),
+		bytes.Replace(fooMod, []byte("foo prob"), []byte("foo ctl prob"), 1),
+		0o666)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	barMod := []byte(`
+$PROBLEM bar prob
+$SIM ONLYSIM (393) SUBPROBLEMS=2
+`)
+	err = os.WriteFile(filepath.Join(dir, "bar.mod"), barMod, 0o666)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	return dir
+}
+
+func TestProbs(tt *testing.T) {
+	t := wrapt.WrapT(tt)
+	dir := setupMods(t)
+
+	t.Run("table output", func(t *wrapt.T) {
+		cmd := exec.Command("bbi", "nonmem", "probs")
+		cmd.Dir = dir
+
+		bs, err := cmd.Output()
+		if err != nil {
+			t.Fatal(err)
+		}
+		out := string(bs)
+
+		t.A.Contains(out, "---")
+		t.A.Contains(out, "foo prob")
+		// FIXME: .mod extension is considered but not .ctl.
+		t.A.NotContains(out, "foo ctl prob")
+		// FIXME: ParseModInfo assumes short "$PROB".
+		t.A.Contains(out, "LEM bar prob")
+	})
+
+	t.Run("json output", func(t *wrapt.T) {
+		cmd := exec.Command("bbi", "nonmem", "probs", "--json")
+		cmd.Dir = dir
+
+		bs, err := cmd.Output()
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		var recs []jsonResult
+		err = json.Unmarshal(bs, &recs)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		t.A.Len(recs, 2)
+
+		for _, rec := range recs {
+			switch rec.RunName {
+			case "foo":
+				t.A.Len(rec.Summary.Tables, 2)
+				t.A.Equal(rec.Summary.Est, []parser.Est{
+					{
+						Method: "$EST METHOD=1 INTERACTION MAXEVAL=9999",
+					},
+					{
+						Method: "$EST METHOD=SAEM NBURN=3000 NITER=2000",
+					},
+				})
+				t.A.True(rec.Summary.Cov.Ok)
+				t.A.False(rec.Summary.Sim.Ok)
+			case "bar":
+				t.A.Len(rec.Summary.Tables, 0)
+				t.A.Len(rec.Summary.Est, 0)
+				t.A.False(rec.Summary.Cov.Ok)
+				t.A.True(rec.Summary.Sim.Ok)
+			default:
+				t.Errorf("expected foo or bar for RunName, got %s", rec.RunName)
+			}
+		}
+	})
+}
+
+func TestProbsErrors(tt *testing.T) {
+	t := wrapt.WrapT(tt)
+
+	cmd := exec.Command("bbi", "nonmem", "probs", "one", "two")
+	_, err := cmd.Output()
+	t.R.Error(err)
+
+	var exitError *exec.ExitError
+	if ok := errors.As(err, &exitError); !ok {
+		t.Fatalf("got error %v; want ExitError", err)
+	}
+
+	t.A.Contains(string(exitError.Stderr), "one directory")
+}