Import modifying runtime abstraction from experimental runtime

This change imports the modifying runtime abstraction from the
experimental branch. This encapsulates the checks for whether
modification is required, and forwards the loaded spec to
the specified modifier. This allows for the same code to be
reused when performing more complex modifications.

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

internal/runtime/runtime_modifier_test.go

@@ -0,0 +1,116 @@
+/*
+# 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 runtime
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/NVIDIA/nvidia-container-toolkit/internal/oci"
+	testlog "github.com/sirupsen/logrus/hooks/test"
+	"github.com/stretchr/testify/require"
+)
+
+func TestExec(t *testing.T) {
+	logger, hook := testlog.NewNullLogger()
+
+	testCases := []struct {
+		description   string
+		shouldModify  bool
+		shouldFlush   bool
+		shouldForward bool
+		args          []string
+		modifyError   error
+		writeError    error
+	}{
+		{
+			description:   "no args forwards",
+			shouldModify:  false,
+			shouldFlush:   false,
+			shouldForward: true,
+		},
+		{
+			description:   "create modifies",
+			args:          []string{"create"},
+			shouldModify:  true,
+			shouldFlush:   true,
+			shouldForward: true,
+		},
+		{
+			description:   "modify error does not write or forward",
+			args:          []string{"create"},
+			modifyError:   fmt.Errorf("error modifying"),
+			shouldModify:  true,
+			shouldFlush:   false,
+			shouldForward: false,
+		},
+		{
+			description:   "write error does not forward",
+			args:          []string{"create"},
+			writeError:    fmt.Errorf("error writing"),
+			shouldModify:  true,
+			shouldFlush:   true,
+			shouldForward: false,
+		},
+	}
+
+	for _, tc := range testCases {
+		hook.Reset()
+
+		t.Run(tc.description, func(t *testing.T) {
+			runtimeMock := &oci.RuntimeMock{}
+			specMock := &oci.SpecMock{
+				ModifyFunc: func(specModifier oci.SpecModifier) error {
+					return tc.modifyError
+				},
+				FlushFunc: func() error {
+					return tc.writeError
+				},
+			}
+
+			shim := NewModifyingRuntimeWrapper(
+				logger,
+				runtimeMock,
+				specMock,
+				// TODO: We should test the interactions with the SpecModifier too
+				nil)
+
+			err := shim.Exec(tc.args)
+			if tc.modifyError != nil || tc.writeError != nil {
+				require.Error(t, err)
+			} else {
+				require.NoError(t, err)
+			}
+
+			if tc.shouldModify {
+				require.Equal(t, 1, len(specMock.ModifyCalls()))
+			} else {
+				require.Equal(t, 0, len(specMock.ModifyCalls()))
+			}
+			if tc.shouldFlush {
+				require.Equal(t, 1, len(specMock.FlushCalls()))
+			} else {
+				require.Equal(t, 0, len(specMock.FlushCalls()))
+			}
+			if tc.shouldForward {
+				require.Equal(t, 1, len(runtimeMock.ExecCalls()))
+			} else {
+				require.Equal(t, 0, len(runtimeMock.ExecCalls()))
+			}
+		})
+	}
+}