diff --git a/metropolis/pkg/erofs/compression_test.go b/metropolis/pkg/erofs/compression_test.go
new file mode 100644
index 0000000..8d5d656
--- /dev/null
+++ b/metropolis/pkg/erofs/compression_test.go
@@ -0,0 +1,91 @@
+// Copyright 2020 The Monogon Project Authors.
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+// 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 erofs
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestEncodeSmallVLEBlock(t *testing.T) {
+	type args struct {
+		vals    [2]uint16
+		blkaddr uint32
+	}
+	tests := []struct {
+		name string
+		args args
+		want [8]byte
+	}{
+		{
+			name: "Reference",
+			args: args{vals: [2]uint16{vleClusterTypeHead | 1527, vleClusterTypeNonhead | 1}, blkaddr: 1},
+			want: [8]byte{0xf7, 0x15, 0x01, 0x20, 0x01, 0x00, 0x00, 0x00},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := encodeSmallVLEBlock(tt.args.vals, tt.args.blkaddr); !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("encodeSmallVLEBlock() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestEncodeBigVLEBlock(t *testing.T) {
+	type args struct {
+		vals    [16]uint16
+		blkaddr uint32
+	}
+	tests := []struct {
+		name string
+		args args
+		want [32]byte
+	}{
+		{
+			name: "Reference",
+			args: args{
+				vals: [16]uint16{
+					vleClusterTypeNonhead | 2,
+					vleClusterTypeHead | 1460,
+					vleClusterTypeNonhead | 1,
+					vleClusterTypeNonhead | 2,
+					vleClusterTypeHead | 2751,
+					vleClusterTypeNonhead | 1,
+					vleClusterTypeNonhead | 2,
+					vleClusterTypeHead | 940,
+					vleClusterTypeNonhead | 1,
+					vleClusterTypeHead | 3142,
+					vleClusterTypeNonhead | 1,
+					vleClusterTypeNonhead | 2,
+					vleClusterTypeHead | 1750,
+					vleClusterTypeNonhead | 1,
+					vleClusterTypeNonhead | 2,
+					vleClusterTypeHead | 683,
+				},
+				blkaddr: 3,
+			},
+			want: [32]byte{0x02, 0x20, 0x6d, 0x15, 0x00, 0x0a, 0x80, 0xbf, 0x5a, 0x00, 0x28, 0x00, 0xb2, 0x4e, 0x01, 0xa0, 0x11, 0x17, 0x00, 0x0a, 0x80, 0xd6, 0x56, 0x00, 0x28, 0x00, 0xae, 0x4a, 0x03, 0x00, 0x00, 0x00}},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := encodeBigVLEBlock(tt.args.vals, tt.args.blkaddr); !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("encodeBigVLEBlock() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}