diff --git a/lib/tests/test_conflicts.rs b/lib/tests/test_conflicts.rs
new file mode 100644
index 000000000..68cceae1b
--- /dev/null
+++ b/lib/tests/test_conflicts.rs
@@ -0,0 +1,253 @@
+// Copyright 2021 Google LLC
+//
+// 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
+//
+// https://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.
+
+use jujutsu_lib::backend::{Conflict, ConflictPart, TreeValue};
+use jujutsu_lib::conflicts::materialize_conflict;
+use jujutsu_lib::repo_path::RepoPath;
+use jujutsu_lib::testutils;
+
+#[test]
+fn test_materialize_conflict_basic() {
+    let settings = testutils::user_settings();
+    let (_temp_dir, repo) = testutils::init_repo(&settings, false);
+
+    let path = RepoPath::from_internal_string("file");
+    let base_id = testutils::write_file(
+        repo.store(),
+        &path,
+        "line 1
+line 2
+line 3
+line 4
+line 5
+",
+    );
+    let left_id = testutils::write_file(
+        repo.store(),
+        &path,
+        "line 1
+line 2
+left
+line 4
+line 5
+",
+    );
+    let right_id = testutils::write_file(
+        repo.store(),
+        &path,
+        "line 1
+line 2
+right
+line 4
+line 5
+",
+    );
+
+    let conflict = Conflict {
+        removes: vec![ConflictPart {
+            value: TreeValue::Normal {
+                id: base_id,
+                executable: false,
+            },
+        }],
+        adds: vec![
+            ConflictPart {
+                value: TreeValue::Normal {
+                    id: left_id,
+                    executable: false,
+                },
+            },
+            ConflictPart {
+                value: TreeValue::Normal {
+                    id: right_id,
+                    executable: false,
+                },
+            },
+        ],
+    };
+    let mut result: Vec<u8> = vec![];
+    materialize_conflict(repo.store(), &path, &conflict, &mut result);
+    assert_eq!(
+        String::from_utf8(result).unwrap().as_str(),
+        "line 1
+line 2
+<<<<<<<
+-------
++++++++
+-line 3
++left
++++++++
+right
+>>>>>>>
+line 4
+line 5
+"
+    );
+}
+
+#[test]
+fn test_materialize_conflict_modify_delete() {
+    let settings = testutils::user_settings();
+    let (_temp_dir, repo) = testutils::init_repo(&settings, false);
+
+    let path = RepoPath::from_internal_string("file");
+    let base_id = testutils::write_file(
+        repo.store(),
+        &path,
+        "line 1
+line 2
+line 3
+line 4
+line 5
+",
+    );
+    let left_id = testutils::write_file(
+        repo.store(),
+        &path,
+        "line 1
+line 2
+left
+line 4
+line 5
+",
+    );
+    let right_id = testutils::write_file(
+        repo.store(),
+        &path,
+        "line 1
+line 2
+line 4
+line 5
+",
+    );
+
+    let conflict = Conflict {
+        removes: vec![ConflictPart {
+            value: TreeValue::Normal {
+                id: base_id,
+                executable: false,
+            },
+        }],
+        adds: vec![
+            ConflictPart {
+                value: TreeValue::Normal {
+                    id: left_id,
+                    executable: false,
+                },
+            },
+            ConflictPart {
+                value: TreeValue::Normal {
+                    id: right_id,
+                    executable: false,
+                },
+            },
+        ],
+    };
+    let mut result: Vec<u8> = vec![];
+    materialize_conflict(repo.store(), &path, &conflict, &mut result);
+    assert_eq!(
+        String::from_utf8(result).unwrap().as_str(),
+        "line 1
+line 2
+<<<<<<<
+-------
++++++++
+-line 3
++left
++++++++
+>>>>>>>
+line 4
+line 5
+"
+    );
+}
+
+#[test]
+fn test_materialize_conflict_delete_modify() {
+    let settings = testutils::user_settings();
+    let (_temp_dir, repo) = testutils::init_repo(&settings, false);
+
+    let path = RepoPath::from_internal_string("file");
+    let base_id = testutils::write_file(
+        repo.store(),
+        &path,
+        "line 1
+line 2
+line 3
+line 4
+line 5
+",
+    );
+    let left_id = testutils::write_file(
+        repo.store(),
+        &path,
+        "line 1
+line 2
+line 4
+line 5
+",
+    );
+    let right_id = testutils::write_file(
+        repo.store(),
+        &path,
+        "line 1
+line 2
+right
+line 4
+line 5
+",
+    );
+
+    let conflict = Conflict {
+        removes: vec![ConflictPart {
+            value: TreeValue::Normal {
+                id: base_id,
+                executable: false,
+            },
+        }],
+        adds: vec![
+            ConflictPart {
+                value: TreeValue::Normal {
+                    id: left_id,
+                    executable: false,
+                },
+            },
+            ConflictPart {
+                value: TreeValue::Normal {
+                    id: right_id,
+                    executable: false,
+                },
+            },
+        ],
+    };
+
+    let mut result: Vec<u8> = vec![];
+    materialize_conflict(repo.store(), &path, &conflict, &mut result);
+    // TODO: There's an extra "+" after "-line 3".
+    assert_eq!(
+        String::from_utf8(result).unwrap().as_str(),
+        "line 1
+line 2
+<<<<<<<
+-------
++++++++
+-line 3
+++++++++
+right
+>>>>>>>
+line 4
+line 5
+"
+    );
+}