tests: pass timestamps via env vars for reproducible hashes

This patch introduces a `JJ_TIMESTAMP` environment variable that lets
us specify the timestamp to use in tests. It also updates the tests to
use it, which means we get to simplify the tests a lot now that that
the hashes are predictable.

lib/src/backend.rs

@@ -233,10 +233,15 @@ pub struct Timestamp {
 
 impl Timestamp {
     pub fn now() -> Self {
-        let now = chrono::offset::Local::now();
+        Self::from_datetime(chrono::offset::Local::now())
+    }
+
+    pub fn from_datetime<Tz: chrono::TimeZone<Offset = chrono::offset::FixedOffset>>(
+        datetime: chrono::DateTime<Tz>,
+    ) -> Self {
         Self {
-            timestamp: MillisSinceEpoch(now.timestamp_millis() as u64),
+            timestamp: MillisSinceEpoch(datetime.timestamp_millis() as u64),
-            tz_offset: now.offset().local_minus_utc() / 60,
+            tz_offset: datetime.offset().local_minus_utc() / 60,
         }
     }
 }

lib/src/commit_builder.rs

@@ -12,8 +12,10 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+use std::env;
 use std::sync::Arc;
 
+use chrono::DateTime;
 use uuid::Uuid;
 
 use crate::backend;
@@ -35,8 +37,13 @@ pub fn new_change_id() -> ChangeId {
 }
 
 pub fn signature(settings: &UserSettings) -> Signature {
-    // TODO: check if it's slow to get the timezone etc for every signature
+    let timestamp = match env::var("JJ_TIMESTAMP") {
-    let timestamp = Timestamp::now();
+        Ok(timestamp_str) => match DateTime::parse_from_rfc3339(&timestamp_str) {
+            Ok(datetime) => Timestamp::from_datetime(datetime),
+            Err(_) => Timestamp::now(),
+        },
+        Err(_) => Timestamp::now(),
+    };
     Signature {
         name: settings.user_name(),
         email: settings.user_email(),

src/testutils.rs

@@ -12,6 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+use std::cell::RefCell;
 use std::path::{Path, PathBuf};
 
 use itertools::Itertools;
@@ -22,6 +23,7 @@ pub struct TestEnvironment {
     _temp_dir: TempDir,
     env_root: PathBuf,
     home_dir: PathBuf,
+    command_number: RefCell<i64>,
 }
 
 impl Default for TestEnvironment {
@@ -33,6 +35,7 @@ impl Default for TestEnvironment {
             _temp_dir: tmp_dir,
             env_root,
             home_dir,
+            command_number: RefCell::new(0),
         }
     }
 }
@@ -43,6 +46,11 @@ impl TestEnvironment {
         cmd.current_dir(current_dir);
         cmd.args(args);
         cmd.env("HOME", self.home_dir.to_str().unwrap());
+        let timestamp = chrono::DateTime::parse_from_rfc3339("2001-02-03T04:05:06+07:00").unwrap();
+        let mut command_number = self.command_number.borrow_mut();
+        *command_number += 1;
+        let timestamp = timestamp + chrono::Duration::seconds(*command_number);
+        cmd.env("JJ_TIMESTAMP", timestamp.to_rfc3339());
         cmd
     }
 

tests/smoke_test.rs

@@ -12,59 +12,64 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-use jujutsu::testutils::{capture_matches, TestEnvironment};
+use jujutsu::testutils::TestEnvironment;
 
 #[test]
 fn smoke_test() {
     let test_env = TestEnvironment::default();
     test_env
-        .jj_cmd(test_env.env_root(), &["init", "repo"])
+        .jj_cmd(test_env.env_root(), &["init", "repo", "--git"])
         .assert()
         .success();
 
     let repo_path = test_env.env_root().join("repo");
     // Check the output of `jj status` right after initializing repo
-    let assert = test_env.jj_cmd(&repo_path, &["status"]).assert().success();
+    let expected_output =
-    let output_regex = "^Parent commit: 000000000000 \nWorking copy : ([[:xdigit:]]+) \nThe \
+        "Parent commit: 000000000000 \nWorking copy : 1d1984a23811 \nThe working copy is clean\n";
-                        working copy is clean\n$";
+    test_env
-    let (_, matches) = capture_matches(assert, output_regex);
+        .jj_cmd(&repo_path, &["status"])
-    let wc_hex_id_empty = matches[0].clone();
+        .assert()
+        .success()
+        .stdout(expected_output);
 
     // Write some files and check the output of `jj status`
     std::fs::write(repo_path.join("file1"), "file1").unwrap();
     std::fs::write(repo_path.join("file2"), "file2").unwrap();
     std::fs::write(repo_path.join("file3"), "file3").unwrap();
 
-    let assert = test_env.jj_cmd(&repo_path, &["status"]).assert().success();
+    // The working copy's ID should have changed
-    let output_regex = "^Parent commit: 000000000000 \nWorking copy : ([[:xdigit:]]+) \nWorking \
+    let expected_output = "Parent commit: 000000000000 \nWorking copy : 5e60c5091e43 \nWorking \
-                        copy changes:
+                           copy changes:
 A file1
 A file2
 A file3
-$";
+";
-    let (_, matches) = capture_matches(assert, output_regex);
+    test_env
-    let wc_hex_id_non_empty = matches[0].clone();
+        .jj_cmd(&repo_path, &["status"])
-
+        .assert()
-    // The working copy's id should have changed
+        .success()
-    assert_ne!(wc_hex_id_non_empty, wc_hex_id_empty);
+        .stdout(expected_output);
 
     // Running `jj status` again gives the same output
-    let assert = test_env.jj_cmd(&repo_path, &["status"]).assert().success();
+    test_env
-    let (_, matches) = capture_matches(assert, output_regex);
+        .jj_cmd(&repo_path, &["status"])
-    let wc_hex_id_again = matches[0].clone();
+        .assert()
-    assert_eq!(wc_hex_id_again, wc_hex_id_non_empty);
+        .success()
+        .stdout(expected_output);
 
     // Add a commit description
-    let assert = test_env
+    let expected_output = "Working copy now at: 6f13b3e41065 add some files\n";
+    test_env
         .jj_cmd(&repo_path, &["describe", "-m", "add some files"])
         .assert()
-        .success();
+        .success()
-    let output_regex = "^Working copy now at: [[:xdigit:]]+ add some files
+        .stdout(expected_output);
-$";
-    assert.stdout(predicates::str::is_match(output_regex).unwrap());
 
     // Close the commit
-    let assert = test_env.jj_cmd(&repo_path, &["close"]).assert().success();
+    let expected_output = "Working copy now at: 6ff8a22d8ce1 \n";
-    let output_regex = "^Working copy now at: [[:xdigit:]]+ \n$";
+    test_env
-    assert.stdout(predicates::str::is_match(output_regex).unwrap());
+        .jj_cmd(&repo_path, &["close"])
+        .assert()
+        .success()
+        .stdout(expected_output);
 }

tests/test_global_opts.rs

@@ -12,62 +12,67 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-use jujutsu::testutils::{get_stdout_string, TestEnvironment};
+use jujutsu::testutils::TestEnvironment;
 
 #[test]
 fn test_no_commit_working_copy() {
     let test_env = TestEnvironment::default();
     test_env
-        .jj_cmd(test_env.env_root(), &["init", "repo"])
+        .jj_cmd(test_env.env_root(), &["init", "repo", "--git"])
         .assert()
         .success();
 
     let repo_path = test_env.env_root().join("repo");
 
     std::fs::write(repo_path.join("file"), "initial").unwrap();
-    let assert = test_env
+    let expected_output = "@ 1e9ff0ea7220c37a1d2c4aab153e238c12ff3cd0
+o 0000000000000000000000000000000000000000
+";
+    test_env
         .jj_cmd(&repo_path, &["log", "-T", "commit_id"])
         .assert()
-        .success();
+        .success()
-    let initial_commit_id_hex = get_stdout_string(&assert);
+        .stdout(expected_output);
 
     // Modify the file. With --no-commit-working-copy, we still get the same commit
     // ID.
     std::fs::write(repo_path.join("file"), "modified").unwrap();
-    let assert = test_env
+    test_env
         .jj_cmd(
             &repo_path,
             &["log", "-T", "commit_id", "--no-commit-working-copy"],
         )
         .assert()
-        .success();
+        .success()
-    let still_initial_commit_id_hex = get_stdout_string(&assert);
+        .stdout(expected_output);
-    assert_eq!(still_initial_commit_id_hex, initial_commit_id_hex);
+
     // But without --no-commit-working-copy, we get a new commit ID.
-    let assert = test_env
+    let expected_output = "@ cc12440b719c67fcd8c55848eb345f67b6e2d9f1
+o 0000000000000000000000000000000000000000
+";
+    test_env
         .jj_cmd(&repo_path, &["log", "-T", "commit_id"])
         .assert()
-        .success();
+        .success()
-    let modified_commit_id_hex = get_stdout_string(&assert);
+        .stdout(expected_output);
-    assert_ne!(modified_commit_id_hex, initial_commit_id_hex);
 }
 
 #[test]
 fn test_repo_arg_with_init() {
     let test_env = TestEnvironment::default();
-    let assert = test_env
+    test_env
         .jj_cmd(test_env.env_root(), &["init", "-R=.", "repo"])
         .assert()
-        .failure();
+        .failure()
-    assert.stdout("Error: '--repository' cannot be used with 'init'\n");
+        .stdout("Error: '--repository' cannot be used with 'init'\n");
 }
 
 #[test]
 fn test_repo_arg_with_git_clone() {
     let test_env = TestEnvironment::default();
-    let assert = test_env
+    test_env
         .jj_cmd(test_env.env_root(), &["git", "clone", "-R=.", "remote"])
         .assert()
-        .failure();
+        .failure()
-    assert.stdout("Error: '--repository' cannot be used with 'git clone'\n");
+        .stdout("Error: '--repository' cannot be used with 'git clone'\n");
 }