Add test for graphics modifier

Signed-off-by: Evan Lezar <elezar@nvidia.com>

internal/modifier/graphics.go

@@ -40,21 +40,8 @@ func NewGraphicsModifier(logger *logrus.Logger, cfg *config.Config, ociSpec oci.
 		return nil, err
 	}
 
-	if devices := image.DevicesFromEnvvars(visibleDevicesEnvvar); len(devices.List()) == 0 {
-		logger.Infof("No modification required; no devices requested")
-		return nil, nil
-	}
-
-	var hasGraphics bool
-	for _, c := range strings.Split(image["NVIDIA_DRIVER_CAPABILITIES"], ",") {
-		if c == "graphics" || c == "all" {
-			hasGraphics = true
-			break
-		}
-	}
-
-	if !hasGraphics {
-		logger.Debugf("Capability %q not selected", "graphics")
+	if required, reason := requiresGraphicsModifier(image); !required {
+		logger.Infof("No graphics modifier required: %v", reason)
 		return nil, nil
 	}
 
@@ -65,3 +52,24 @@ func NewGraphicsModifier(logger *logrus.Logger, cfg *config.Config, ociSpec oci.
 
 	return NewModifierFromDiscoverer(logger, d)
 }
+
+// requiresGraphicsModifier determines whether a graphics modifier is required.
+func requiresGraphicsModifier(cudaImage image.CUDA) (bool, string) {
+	if devices := cudaImage.DevicesFromEnvvars(visibleDevicesEnvvar); len(devices.List()) == 0 {
+		return false, "no devices requested"
+	}
+
+	var hasGraphics bool
+	for _, c := range strings.Split(cudaImage["NVIDIA_DRIVER_CAPABILITIES"], ",") {
+		if c == "graphics" || c == "all" {
+			hasGraphics = true
+			break
+		}
+	}
+
+	if !hasGraphics {
+		return false, fmt.Sprintf("Capability %q not selected", "graphics")
+	}
+
+	return true, ""
+}

internal/modifier/graphics_test.go

@@ -0,0 +1,88 @@
+/**
+# Copyright (c) 2022, NVIDIA CORPORATION.  All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+**/
+
+package modifier
+
+import (
+	"testing"
+
+	"github.com/NVIDIA/nvidia-container-toolkit/internal/config/image"
+	"github.com/stretchr/testify/require"
+)
+
+func TestGraphicsModifier(t *testing.T) {
+	testCases := []struct {
+		description      string
+		cudaImage        image.CUDA
+		expectedRequired bool
+	}{
+		{
+			description: "empty image does not create modifier",
+		},
+		{
+			description: "devices with no capabilities does not create modifier",
+			cudaImage: image.CUDA{
+				"NVIDIA_VISIBLE_DEVICES": "all",
+			},
+		},
+		{
+			description: "devices with no non-graphics does not create modifier",
+			cudaImage: image.CUDA{
+				"NVIDIA_VISIBLE_DEVICES":     "all",
+				"NVIDIA_DRIVER_CAPABILITIES": "compute",
+			},
+		},
+		{
+			description: "devices with all capabilities creates modifier",
+			cudaImage: image.CUDA{
+				"NVIDIA_VISIBLE_DEVICES":     "all",
+				"NVIDIA_DRIVER_CAPABILITIES": "all",
+			},
+			expectedRequired: true,
+		},
+		{
+			description: "devices with graphics capability creates modifier",
+			cudaImage: image.CUDA{
+				"NVIDIA_VISIBLE_DEVICES":     "all",
+				"NVIDIA_DRIVER_CAPABILITIES": "graphics",
+			},
+			expectedRequired: true,
+		},
+		{
+			description: "devices with compute,graphics capability creates modifier",
+			cudaImage: image.CUDA{
+				"NVIDIA_VISIBLE_DEVICES":     "all",
+				"NVIDIA_DRIVER_CAPABILITIES": "compute,graphics",
+			},
+			expectedRequired: true,
+		},
+		{
+			description: "devices with display,graphics capability creates modifier",
+			cudaImage: image.CUDA{
+				"NVIDIA_VISIBLE_DEVICES":     "all",
+				"NVIDIA_DRIVER_CAPABILITIES": "display,graphics",
+			},
+			expectedRequired: true,
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.description, func(t *testing.T) {
+			required, _ := requiresGraphicsModifier(tc.cudaImage)
+			require.EqualValues(t, tc.expectedRequired, required)
+		})
+	}
+}