You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: mutate_test.go
    path of file: ./repos/buildkit/sourcepolicy
    
    the code of the file until where you have to start completion: package sourcepolicy

import (
	"context"
	"testing"

	"github.com/moby/buildkit/solver/pb"
	spb "github.com/moby/buildkit/sourcepolicy/pb"
	"github.com/stretchr/testify/require"
)

func TestMutate(t *testing.T) {
	type testCaseOp struct {
		op          *pb.Op
		rule        *spb.Rule
		expected    bool
		expectedOp  *pb.Op
		expectedErr string
	}

	testCases := []testCaseOp{
		{
			op: &pb.Op{
				Op: &pb.Op_Source{
					Source: &pb.SourceOp{
						Identifier: "docker-image://docker.io/library/busybox:1.34.1-uclibc",
					},
				},
			},
			rule: &spb.Rule{
				Selector: &spb.Selector{
					Identifier: "docker-image://docker.io/library/busybox:1.34.1-uclibc",
				},
				Updates: &spb.Update{
					Identifier: "docker-image://docker.io/library/busybox:1.34.1-uclibc@sha256:3614ca5eacf0a3a1bcc361c939202a974b4902b9334ff36eb29ffe9011aaad83",
				},
			},
			expected: true,
			expectedOp: &pb.Op{
				Op: &pb.Op_Source{
					Source: &pb.SourceOp{
						Identifier: "docker-image://docker.io/library/busybox:1.34.1-uclibc@sha256:3614ca5eacf0a3a1bcc361c939202a974b4902b9334ff36eb29ffe9011aaad83",
					},
				},
			},
		},
		{
			op: &pb.Op{
				Op: &pb.Op_Source{
					Source: &pb.SourceOp{
						Identifier: "docker-image://docker.io/library/busybox",
					},
				},
			},
			rule: &spb.Rule{
				Selector: &spb.Selector{
					Identifier: "docker-image://docker.io/library/busybox",
				},
				Updates: &spb.Update{
					Identifier: "docker-image://docker.io/library/busybox:latest@sha256:3614ca5eacf0a3a1bcc361c939202a974b4902b9334ff36eb29ffe9011aaad83",
				},
			},
			expected: true,
			expectedOp: &pb.Op{
				Op: &pb.Op_Source{
					Source: &pb.SourceOp{
						Identifier: "docker-image://docker.io/library/busybox:latest@sha256:3614ca5eacf0a3a1bcc361c939202a974b490
    
func TestMutate(t *testing.T) {
	type testCaseOp struct {
		op          *pb.Op
		rule        *spb.Rule
		expected    bool
		expectedOp  *pb.Op
		expectedErr string
	}

	testCases := []testCaseOp{
		{
			op: &pb.Op{
				Op: &pb.Op_Source{
					Source: &pb.SourceOp{
						Identifier: "docker-image://docker.io/library/busybox:1.34.1-uclibc",
					},
				},
			},
			rule: &spb.Rule{
				Selector: &spb.Selector{
					Identifier: "docker-image://docker.io/library/busybox:1.34.1-uclibc",
				},
				Updates: &spb.Update{
					Identifier: "docker-image://docker.io/library/busybox:1.34.1-uclibc@sha256:3614ca5eacf0a3a1bcc361c939202a974b4902b9334ff36eb29ffe9011aaad83",
				},
			},
			expected: true,
			expectedOp: &pb.Op{
				Op: &pb.Op_Source{
					Source: &pb.SourceOp{
						Identifier: "docker-image://docker.io/library/busybox:1.34.1-uclibc@sha256:3614ca5eacf0a3a1bcc361c939202a974b4902b9334ff36eb29ffe9011aaad83",
					},
				},
			},
		},
		{
			op: &pb.Op{
				Op: &pb.Op_Source{
					Source: &pb.SourceOp{
						Identifier: "docker-image://docker.io/library/busybox",
					},
				},
			},
			rule: &spb.Rule{
				Selector: &spb.Selector{
					Identifier: "docker-image://docker.io/library/busybox",
				},
				Updates: &spb.Update{
					Identifier: "docker-image://docker.io/library/busybox:latest@sha256:3614ca5eacf0a3a1bcc361c939202a974b4902b9334ff36eb29ffe9011aaad83",
				},
			},
			expected: true,
			expectedOp: &pb.Op{
				Op: &pb.Op_Source{
					Source: &pb.SourceOp{
						Identifier: "docker-image://docker.io/library/busybox:latest@sha256:3614ca5eacf0a3a1bcc361c939202a974b4902b9334ff36eb29ffe9011aaad83",
					},
				},
			},
		},
		{
			// Discard the existing digest that might have been resolved by the Dockerfile frontend's MetaResolver.
			op: &pb.Op{
				Op: &pb.Op_Source{
					Source: &pb.SourceOp{
						Identifier: "docker-image://docker.io/library/busybox:latest@sha256:aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
					},
				},
			},
			rule: &spb.Rule{
				Selector: &spb.Selector{
					Identifier: "docker-image://docker.io/library/busybox:latest*",
				},
				Updates: &spb.Update{
					Identifier: "docker-image://docker.io/library/busybox:latest@sha256:3614ca5eacf0a3a1bcc361c939202a974b4902b9334ff36eb29ffe9011aaad83",
				},
			},
			expected: true,
			expectedOp: &pb.Op{
				Op: &pb.Op_Source{
					Source: &pb.SourceOp{
						Identifier: "docker-image://docker.io/library/busybox:latest@sha256:3614ca5eacf0a3a1bcc361c939202a974b4902b9334ff36eb29ffe9011aaad83",
					},
				},
			},
		},
		{
			op: &pb.Op{
				Op: &pb.Op_Source{
					Source: &pb.SourceOp{
						Identifier: "https://raw.githubusercontent.com/moby/buildkit/v0.10.1/README.md",
					},
				},
			},
			rule: &spb.Rule{
				Selector: &spb.Selector{},
				Updates: &spb.Update{
					Identifier: "https://raw.githubusercontent.com/moby/buildkit/v0.10.1/README.md",
					Attrs:      map[string]string{pb.AttrHTTPChecksum: "sha256:6e4b94fc270e708e1068be28bd3551dc6917a4fc5a61293d51bb36e6b75c4b53"},
				},
			},
			expected: true,
			expectedOp: &pb.Op{
				Op: &pb.Op_Source{
					Source: &pb.SourceOp{
						Identifier: "https://raw.githubusercontent.com/moby/buildkit/v0.10.1/README.md",
						Attrs: map[string]string{
							pb.AttrHTTPChecksum: "sha256:6e4b94fc270e708e1068be28bd3551dc6917a4fc5a61293d51bb36e6b75c4b53",
						},
					},
				},
			},
		},
	}

	ctx := context.Background()
	for _, tc := range testCases {
		op := *tc.op
		t.Run(op.String(), func(t *testing.T) {
			src := op.GetSource()
			mutated, err := mutate(ctx, src, tc.rule, &selectorCache{Selector: tc.rule.Selector}, src.GetIdentifier())
			require.Equal(t, tc.expected, mutated)
			if tc.expectedErr != "" {
				require.Error(t, err, tc.expectedErr)
			} else {
				require.Equal(t, tc.expectedOp, &op)
			}
		})
	}
}