diff --git a/Cargo.toml b/Cargo.toml
index 9c9fe7cbb..6e829363d 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -18,6 +18,9 @@ quick-error = "1.2.2"
 rand = "0.5.4"
 fxhash = "0.2.1"
 
+[dev-dependencies]
+env_logger = "0.5.12"
+
 [badges]
 travis-ci = { repository = "pingcap/raft-rs" }
 
diff --git a/tests/cases/test_raft.rs b/tests/cases/test_raft.rs
index 5b385c548..77ace7b9e 100644
--- a/tests/cases/test_raft.rs
+++ b/tests/cases/test_raft.rs
@@ -37,6 +37,7 @@ use raft::eraftpb::{
     Snapshot,
 };
 use rand;
+use env_logger;
 
 use raft::storage::MemStorage;
 use raft::*;
@@ -425,6 +426,7 @@ impl Network {
 
 #[test]
 fn test_progress_become_probe() {
+    let _ = env_logger::try_init();
     let matched = 1u64;
     let mut tests = vec![
         (
@@ -460,6 +462,7 @@ fn test_progress_become_probe() {
 
 #[test]
 fn test_progress_become_replicate() {
+    let _ = env_logger::try_init();
     let mut p = new_progress(ProgressState::Probe, 1, 5, 0, 256);
     p.become_replicate();
 
@@ -470,6 +473,7 @@ fn test_progress_become_replicate() {
 
 #[test]
 fn test_progress_become_snapshot() {
+    let _ = env_logger::try_init();
     let mut p = new_progress(ProgressState::Probe, 1, 5, 0, 256);
     p.become_snapshot(10);
     assert_eq!(p.state, ProgressState::Snapshot);
@@ -479,6 +483,7 @@ fn test_progress_become_snapshot() {
 
 #[test]
 fn test_progress_update() {
+    let _ = env_logger::try_init();
     let (prev_m, prev_n) = (3u64, 5u64);
     let tests = vec![
         (prev_m - 1, prev_m, prev_n, false),
@@ -507,6 +512,7 @@ fn test_progress_update() {
 
 #[test]
 fn test_progress_maybe_decr() {
+    let _ = env_logger::try_init();
     let tests = vec![
         // state replicate and rejected is not greater than match
         (ProgressState::Replicate, 5, 10, 5, 5, false, 10),
@@ -546,6 +552,7 @@ fn test_progress_maybe_decr() {
 
 #[test]
 fn test_progress_is_paused() {
+    let _ = env_logger::try_init();
     let tests = vec![
         (ProgressState::Probe, false, false),
         (ProgressState::Probe, true, true),
@@ -571,6 +578,7 @@ fn test_progress_is_paused() {
 // will reset progress.paused.
 #[test]
 fn test_progress_resume() {
+    let _ = env_logger::try_init();
     let mut p = Progress {
         next_idx: 2,
         paused: true,
@@ -587,6 +595,7 @@ fn test_progress_resume() {
 // heartbeat response.
 #[test]
 fn test_progress_resume_by_heartbeat_resp() {
+    let _ = env_logger::try_init();
     let mut raft = new_test_raft(1, vec![1, 2], 5, 1, new_storage());
     raft.become_candidate();
     raft.become_leader();
@@ -604,6 +613,7 @@ fn test_progress_resume_by_heartbeat_resp() {
 
 #[test]
 fn test_progress_paused() {
+    let _ = env_logger::try_init();
     let mut raft = new_test_raft(1, vec![1, 2], 5, 1, new_storage());
     raft.become_candidate();
     raft.become_leader();
@@ -623,11 +633,13 @@ fn test_progress_paused() {
 
 #[test]
 fn test_leader_election() {
+    let _ = env_logger::try_init();
     test_leader_election_with_config(false);
 }
 
 #[test]
 fn test_leader_election_pre_vote() {
+    let _ = env_logger::try_init();
     test_leader_election_with_config(true);
 }
 
@@ -702,11 +714,13 @@ fn test_leader_election_with_config(pre_vote: bool) {
 
 #[test]
 fn test_leader_cycle() {
+    let _ = env_logger::try_init();
     test_leader_cycle_with_config(false)
 }
 
 #[test]
 fn test_leader_cycle_pre_vote() {
+    let _ = env_logger::try_init();
     test_leader_cycle_with_config(true)
 }
 
@@ -743,11 +757,13 @@ fn test_leader_cycle_with_config(pre_vote: bool) {
 
 #[test]
 fn test_leader_election_overwrite_newer_logs() {
+    let _ = env_logger::try_init();
     test_leader_election_overwrite_newer_logs_with_config(false);
 }
 
 #[test]
 fn test_leader_election_overwrite_newer_logs_pre_vote() {
+    let _ = env_logger::try_init();
     test_leader_election_overwrite_newer_logs_with_config(true);
 }
 
@@ -823,11 +839,13 @@ fn test_leader_election_overwrite_newer_logs_with_config(pre_vote: bool) {
 
 #[test]
 fn test_vote_from_any_state() {
+    let _ = env_logger::try_init();
     test_vote_from_any_state_for_type(MessageType::MsgRequestVote);
 }
 
 #[test]
 fn test_prevote_from_any_state() {
+    let _ = env_logger::try_init();
     test_vote_from_any_state_for_type(MessageType::MsgRequestPreVote);
 }
 
@@ -935,6 +953,7 @@ fn test_vote_from_any_state_for_type(vt: MessageType) {
 
 #[test]
 fn test_log_replicatioin() {
+    let _ = env_logger::try_init();
     let mut tests = vec![
         (
             Network::new(vec![None, None, None]),
@@ -990,6 +1009,7 @@ fn test_log_replicatioin() {
 
 #[test]
 fn test_single_node_commit() {
+    let _ = env_logger::try_init();
     let mut tt = Network::new(vec![None]);
     tt.send(vec![new_message(1, 1, MessageType::MsgHup, 0)]);
     tt.send(vec![new_message(1, 1, MessageType::MsgPropose, 1)]);
@@ -1003,6 +1023,7 @@ fn test_single_node_commit() {
 // filtered.
 #[test]
 fn test_cannot_commit_without_new_term_entry() {
+    let _ = env_logger::try_init();
     let mut tt = Network::new(vec![None, None, None, None, None]);
     tt.send(vec![new_message(1, 1, MessageType::MsgHup, 0)]);
 
@@ -1040,6 +1061,7 @@ fn test_cannot_commit_without_new_term_entry() {
 // when leader changes, no new proposal comes in.
 #[test]
 fn test_commit_without_new_term_entry() {
+    let _ = env_logger::try_init();
     let mut tt = Network::new(vec![None, None, None, None, None]);
     tt.send(vec![new_message(1, 1, MessageType::MsgHup, 0)]);
 
@@ -1066,6 +1088,7 @@ fn test_commit_without_new_term_entry() {
 
 #[test]
 fn test_dueling_candidates() {
+    let _ = env_logger::try_init();
     let a = new_test_raft(1, vec![1, 2, 3], 10, 1, new_storage());
     let b = new_test_raft(2, vec![1, 2, 3], 10, 1, new_storage());
     let c = new_test_raft(3, vec![1, 2, 3], 10, 1, new_storage());
@@ -1119,6 +1142,7 @@ fn test_dueling_candidates() {
 
 #[test]
 fn test_dueling_pre_candidates() {
+    let _ = env_logger::try_init();
     let a = new_test_raft_with_prevote(1, vec![1, 2, 3], 10, 1, new_storage(), true);
     let b = new_test_raft_with_prevote(2, vec![1, 2, 3], 10, 1, new_storage(), true);
     let c = new_test_raft_with_prevote(3, vec![1, 2, 3], 10, 1, new_storage(), true);
@@ -1168,6 +1192,7 @@ fn test_dueling_pre_candidates() {
 
 #[test]
 fn test_candidate_concede() {
+    let _ = env_logger::try_init();
     let mut tt = Network::new(vec![None, None, None]);
     tt.isolate(1);
 
@@ -1202,6 +1227,7 @@ fn test_candidate_concede() {
 
 #[test]
 fn test_single_node_candidate() {
+    let _ = env_logger::try_init();
     let mut tt = Network::new(vec![None]);
     tt.send(vec![new_message(1, 1, MessageType::MsgHup, 0)]);
 
@@ -1210,6 +1236,7 @@ fn test_single_node_candidate() {
 
 #[test]
 fn test_sinle_node_pre_candidate() {
+    let _ = env_logger::try_init();
     let mut tt = Network::new_with_config(vec![None], true);
     tt.send(vec![new_message(1, 1, MessageType::MsgHup, 0)]);
 
@@ -1218,6 +1245,7 @@ fn test_sinle_node_pre_candidate() {
 
 #[test]
 fn test_old_messages() {
+    let _ = env_logger::try_init();
     let mut tt = Network::new(vec![None, None, None]);
     // make 0 leader @ term 3
     tt.send(vec![new_message(1, 1, MessageType::MsgHup, 0)]);
@@ -1251,6 +1279,7 @@ fn test_old_messages() {
 
 #[test]
 fn test_proposal() {
+    let _ = env_logger::try_init();
     let mut tests = vec![
         (Network::new(vec![None, None, None]), true),
         (Network::new(vec![None, None, NOP_STEPPER]), true),
@@ -1297,6 +1326,7 @@ fn test_proposal() {
 
 #[test]
 fn test_proposal_by_proxy() {
+    let _ = env_logger::try_init();
     let mut tests = vec![
         Network::new(vec![None, None, None]),
         Network::new(vec![None, None, NOP_STEPPER]),
@@ -1327,6 +1357,7 @@ fn test_proposal_by_proxy() {
 
 #[test]
 fn test_commit() {
+    let _ = env_logger::try_init();
     let mut tests = vec![
         // single
         (vec![1u64], vec![empty_entry(1, 1)], 1u64, 1u64),
@@ -1420,6 +1451,7 @@ fn test_commit() {
 
 #[test]
 fn test_pass_election_timeout() {
+    let _ = env_logger::try_init();
     let tests = vec![
         (5, 0f64, false),
         (10, 0.1, true),
@@ -1453,6 +1485,7 @@ fn test_pass_election_timeout() {
 // actual stepX function.
 #[test]
 fn test_step_ignore_old_term_msg() {
+    let _ = env_logger::try_init();
     let mut sm = new_test_raft(1, vec![1], 10, 1, new_storage());
     let panic_before_step_state =
         Box::new(|_: &Message| panic!("before step state function hook called unexpectedly"));
@@ -1471,6 +1504,7 @@ fn test_step_ignore_old_term_msg() {
 // 3. If leaderCommit > commitIndex, set commitIndex = min(leaderCommit, index of last new entry).
 #[test]
 fn test_handle_msg_append() {
+    let _ = env_logger::try_init();
     let nm = |term, log_term, index, commit, ents: Option<Vec<(u64, u64)>>| {
         let mut m = Message::new();
         m.set_msg_type(MessageType::MsgAppend);
@@ -1540,6 +1574,7 @@ fn test_handle_msg_append() {
 // test_handle_heartbeat ensures that the follower commits to the commit in the message.
 #[test]
 fn test_handle_heartbeat() {
+    let _ = env_logger::try_init();
     let commit = 2u64;
     let nw = |f, to, term, commit| {
         let mut m = new_message(f, to, MessageType::MsgHeartbeat, 0);
@@ -1584,6 +1619,7 @@ fn test_handle_heartbeat() {
 // test_handle_heartbeat_resp ensures that we re-send log entries when we get a heartbeat response.
 #[test]
 fn test_handle_heartbeat_resp() {
+    let _ = env_logger::try_init();
     let store = new_storage();
     store
         .wl()
@@ -1627,6 +1663,7 @@ fn test_handle_heartbeat_resp() {
 // related issue: https://github.com/coreos/etcd/issues/7571
 #[test]
 fn test_raft_frees_read_only_mem() {
+    let _ = env_logger::try_init();
     let mut sm = new_test_raft(1, vec![1, 2], 5, 1, new_storage());
     sm.become_candidate();
     sm.become_leader();
@@ -1668,6 +1705,7 @@ fn test_raft_frees_read_only_mem() {
 // MsgAppResp.
 #[test]
 fn test_msg_append_response_wait_reset() {
+    let _ = env_logger::try_init();
     let mut sm = new_test_raft(1, vec![1, 2, 3], 5, 1, new_storage());
     sm.become_candidate();
     sm.become_leader();
@@ -1713,6 +1751,7 @@ fn test_msg_append_response_wait_reset() {
 
 #[test]
 fn test_recv_msg_request_vote() {
+    let _ = env_logger::try_init();
     test_recv_msg_request_vote_for_type(MessageType::MsgRequestVote);
 }
 
@@ -1793,6 +1832,7 @@ fn test_recv_msg_request_vote_for_type(msg_type: MessageType) {
 
 #[test]
 fn test_state_transition() {
+    let _ = env_logger::try_init();
     let mut tests = vec![
         (
             StateRole::Follower,
@@ -1905,6 +1945,7 @@ fn test_state_transition() {
 
 #[test]
 fn test_all_server_stepdown() {
+    let _ = env_logger::try_init();
     let mut tests = vec![
         (StateRole::Follower, StateRole::Follower, 3, 0),
         (StateRole::PreCandidate, StateRole::Follower, 3, 0),
@@ -1966,11 +2007,13 @@ fn test_all_server_stepdown() {
 
 #[test]
 fn test_candidate_reset_term_msg_heartbeat() {
+    let _ = env_logger::try_init();
     test_candidate_reset_term(MessageType::MsgHeartbeat)
 }
 
 #[test]
 fn test_candidate_reset_term_msg_append() {
+    let _ = env_logger::try_init();
     test_candidate_reset_term(MessageType::MsgAppend)
 }
 
@@ -2031,6 +2074,7 @@ fn test_candidate_reset_term(message_type: MessageType) {
 
 #[test]
 fn test_leader_stepdown_when_quorum_active() {
+    let _ = env_logger::try_init();
     let mut sm = new_test_raft(1, vec![1, 2, 3], 5, 1, new_storage());
     sm.check_quorum = true;
     sm.become_candidate();
@@ -2048,6 +2092,7 @@ fn test_leader_stepdown_when_quorum_active() {
 
 #[test]
 fn test_leader_stepdown_when_quorum_lost() {
+    let _ = env_logger::try_init();
     let mut sm = new_test_raft(1, vec![1, 2, 3], 5, 1, new_storage());
 
     sm.check_quorum = true;
@@ -2064,6 +2109,7 @@ fn test_leader_stepdown_when_quorum_lost() {
 
 #[test]
 fn test_leader_superseding_with_check_quorum() {
+    let _ = env_logger::try_init();
     let mut a = new_test_raft(1, vec![1, 2, 3], 10, 1, new_storage());
     let mut b = new_test_raft(2, vec![1, 2, 3], 10, 1, new_storage());
     let mut c = new_test_raft(3, vec![1, 2, 3], 10, 1, new_storage());
@@ -2104,6 +2150,7 @@ fn test_leader_superseding_with_check_quorum() {
 
 #[test]
 fn test_leader_election_with_check_quorum() {
+    let _ = env_logger::try_init();
     let mut a = new_test_raft(1, vec![1, 2, 3], 10, 1, new_storage());
     let mut b = new_test_raft(2, vec![1, 2, 3], 10, 1, new_storage());
     let mut c = new_test_raft(3, vec![1, 2, 3], 10, 1, new_storage());
@@ -2165,6 +2212,7 @@ fn test_leader_election_with_check_quorum() {
 // leader is expected to step down and adopt the candidate's term
 #[test]
 fn test_free_stuck_candidate_with_check_quorum() {
+    let _ = env_logger::try_init();
     let mut a = new_test_raft(1, vec![1, 2, 3], 10, 1, new_storage());
     let mut b = new_test_raft(2, vec![1, 2, 3], 10, 1, new_storage());
     let mut c = new_test_raft(3, vec![1, 2, 3], 10, 1, new_storage());
@@ -2218,6 +2266,7 @@ fn test_free_stuck_candidate_with_check_quorum() {
 
 #[test]
 fn test_non_promotable_voter_which_check_quorum() {
+    let _ = env_logger::try_init();
     let mut a = new_test_raft(1, vec![1, 2], 10, 1, new_storage());
     let mut b = new_test_raft(2, vec![1], 10, 1, new_storage());
 
@@ -2258,6 +2307,7 @@ fn test_non_promotable_voter_which_check_quorum() {
 /// to step down.
 #[test]
 fn test_disruptive_follower() {
+    let _ = env_logger::try_init();
     let mut n1 = new_test_raft(1, vec![1, 2, 3], 10, 1, new_storage());
     let mut n2 = new_test_raft(2, vec![1, 2, 3], 10, 1, new_storage());
     let mut n3 = new_test_raft(3, vec![1, 2, 3], 10, 1, new_storage());
@@ -2348,6 +2398,7 @@ fn test_disruptive_follower() {
 /// current leader to step down, thus less disruptions.
 #[test]
 fn test_disruptive_follower_pre_vote() {
+    let _ = env_logger::try_init();
     let mut n1 = new_test_raft_with_prevote(1, vec![1, 2, 3], 10, 1, new_storage(), true);
     let mut n2 = new_test_raft_with_prevote(2, vec![1, 2, 3], 10, 1, new_storage(), true);
     let mut n3 = new_test_raft_with_prevote(3, vec![1, 2, 3], 10, 1, new_storage(), true);
@@ -2398,6 +2449,7 @@ fn test_disruptive_follower_pre_vote() {
 
 #[test]
 fn test_read_only_option_safe() {
+    let _ = env_logger::try_init();
     let a = new_test_raft(1, vec![1, 2, 3], 10, 1, new_storage());
     let b = new_test_raft(2, vec![1, 2, 3], 10, 1, new_storage());
     let c = new_test_raft(3, vec![1, 2, 3], 10, 1, new_storage());
@@ -2467,6 +2519,7 @@ fn test_read_only_option_safe() {
 
 #[test]
 fn test_read_only_option_lease() {
+    let _ = env_logger::try_init();
     let mut a = new_test_raft(1, vec![1, 2, 3], 10, 1, new_storage());
     let mut b = new_test_raft(2, vec![1, 2, 3], 10, 1, new_storage());
     let mut c = new_test_raft(3, vec![1, 2, 3], 10, 1, new_storage());
@@ -2542,6 +2595,7 @@ fn test_read_only_option_lease() {
 
 #[test]
 fn test_read_only_option_lease_without_check_quorum() {
+    let _ = env_logger::try_init();
     let mut a = new_test_raft(1, vec![1, 2, 3], 10, 1, new_storage());
     let mut b = new_test_raft(2, vec![1, 2, 3], 10, 1, new_storage());
     let mut c = new_test_raft(3, vec![1, 2, 3], 10, 1, new_storage());
@@ -2573,6 +2627,7 @@ fn test_read_only_option_lease_without_check_quorum() {
 // when it commits at least one log entry at it term.
 #[test]
 fn test_read_only_for_new_leader() {
+    let _ = env_logger::try_init();
     let heartbeat_ticks = 1;
     let node_configs = vec![(1, 1, 1, 0), (2, 2, 2, 2), (3, 2, 2, 2)];
     let mut peers = vec![];
@@ -2649,6 +2704,7 @@ fn test_read_only_for_new_leader() {
 
 #[test]
 fn test_leader_append_response() {
+    let _ = env_logger::try_init();
     // initial progress: match = 0; next = 3
     let mut tests = vec![
         (3, true, 0, 3, 0, 0, 0), // stale resp; no replies
@@ -2717,6 +2773,7 @@ fn test_leader_append_response() {
 // send a MsgApp with m.Index = 0, m.LogTerm=0 and empty entries.
 #[test]
 fn test_bcast_beat() {
+    let _ = env_logger::try_init();
     let offset = 1000u64;
     // make a state machine with log.offset = 1000
     let s = new_snapshot(offset, 1, vec![1, 2, 3]);
@@ -2792,6 +2849,7 @@ fn test_bcast_beat() {
 // tests the output of the statemachine when receiving MsgBeat
 #[test]
 fn test_recv_msg_beat() {
+    let _ = env_logger::try_init();
     let mut tests = vec![
         (StateRole::Leader, 2),
         // candidate and follower should ignore MsgBeat
@@ -2826,6 +2884,7 @@ fn test_recv_msg_beat() {
 
 #[test]
 fn test_leader_increase_next() {
+    let _ = env_logger::try_init();
     let previous_ents = vec![empty_entry(1, 1), empty_entry(1, 2), empty_entry(1, 3)];
     let mut tests = vec![
         // state replicate; optimistically increase next
@@ -2861,6 +2920,7 @@ fn test_leader_increase_next() {
 
 #[test]
 fn test_send_append_for_progress_probe() {
+    let _ = env_logger::try_init();
     let mut r = new_test_raft(1, vec![1, 2], 10, 1, new_storage());
     r.become_candidate();
     r.become_leader();
@@ -2911,6 +2971,7 @@ fn test_send_append_for_progress_probe() {
 
 #[test]
 fn test_send_append_for_progress_replicate() {
+    let _ = env_logger::try_init();
     let mut r = new_test_raft(1, vec![1, 2], 10, 1, new_storage());
     r.become_candidate();
     r.become_leader();
@@ -2926,6 +2987,7 @@ fn test_send_append_for_progress_replicate() {
 
 #[test]
 fn test_send_append_for_progress_snapshot() {
+    let _ = env_logger::try_init();
     let mut r = new_test_raft(1, vec![1, 2], 10, 1, new_storage());
     r.become_candidate();
     r.become_leader();
@@ -2941,6 +3003,7 @@ fn test_send_append_for_progress_snapshot() {
 
 #[test]
 fn test_recv_msg_unreachable() {
+    let _ = env_logger::try_init();
     let previous_ents = vec![empty_entry(1, 1), empty_entry(1, 2), empty_entry(1, 3)];
     let s = new_storage();
     s.wl().append(&previous_ents).expect("");
@@ -2965,6 +3028,7 @@ fn test_recv_msg_unreachable() {
 
 #[test]
 fn test_restore() {
+    let _ = env_logger::try_init();
     // magic number
     let s = new_snapshot(11, 11, vec![1, 2, 3]);
 
@@ -2984,6 +3048,7 @@ fn test_restore() {
 
 #[test]
 fn test_restore_ignore_snapshot() {
+    let _ = env_logger::try_init();
     let previous_ents = vec![empty_entry(1, 1), empty_entry(1, 2), empty_entry(1, 3)];
     let commit = 1u64;
     let mut sm = new_test_raft(1, vec![1, 2], 10, 1, new_storage());
@@ -3004,6 +3069,7 @@ fn test_restore_ignore_snapshot() {
 
 #[test]
 fn test_provide_snap() {
+    let _ = env_logger::try_init();
     // restore the state machine from a snapshot so it has a compacted log and a snapshot
     let s = new_snapshot(11, 11, vec![1, 2]); // magic number
 
@@ -3027,6 +3093,7 @@ fn test_provide_snap() {
 
 #[test]
 fn test_ignore_providing_snapshot() {
+    let _ = env_logger::try_init();
     // restore the state machine from a snapshot so it has a compacted log and a snapshot
     let s = new_snapshot(11, 11, vec![1, 2]); // magic number
     let mut sm = new_test_raft(1, vec![1], 10, 1, new_storage());
@@ -3048,6 +3115,7 @@ fn test_ignore_providing_snapshot() {
 
 #[test]
 fn test_restore_from_snap_msg() {
+    let _ = env_logger::try_init();
     let s = new_snapshot(11, 11, vec![1, 2]); // magic number
     let mut sm = new_test_raft(2, vec![1, 2], 10, 1, new_storage());
     let mut m = new_message(1, 0, MessageType::MsgSnapshot, 0);
@@ -3063,6 +3131,7 @@ fn test_restore_from_snap_msg() {
 
 #[test]
 fn test_slow_node_restore() {
+    let _ = env_logger::try_init();
     let mut nt = Network::new(vec![None, None, None]);
     nt.send(vec![new_message(1, 1, MessageType::MsgHup, 0)]);
 
@@ -3107,6 +3176,7 @@ fn test_slow_node_restore() {
 // it appends the entry to log and sets pendingConf to be true.
 #[test]
 fn test_step_config() {
+    let _ = env_logger::try_init();
     // a raft that cannot make progress
     let mut r = new_test_raft(1, vec![1, 2], 10, 1, new_storage());
     r.become_candidate();
@@ -3125,6 +3195,7 @@ fn test_step_config() {
 // the proposal to noop and keep its original state.
 #[test]
 fn test_step_ignore_config() {
+    let _ = env_logger::try_init();
     // a raft that cannot make progress
     let mut r = new_test_raft(1, vec![1, 2], 10, 1, new_storage());
     r.become_candidate();
@@ -3151,6 +3222,7 @@ fn test_step_ignore_config() {
 // based on uncommitted entries.
 #[test]
 fn test_new_leader_pending_config() {
+    let _ = env_logger::try_init();
     let mut tests = vec![(false, 0), (true, 1)];
     for (i, (add_entry, wpending_index)) in tests.drain(..).enumerate() {
         let mut r = new_test_raft(1, vec![1, 2], 10, 1, new_storage());
@@ -3174,6 +3246,7 @@ fn test_new_leader_pending_config() {
 // test_add_node tests that add_node could update nodes correctly.
 #[test]
 fn test_add_node() {
+    let _ = env_logger::try_init();
     let mut r = new_test_raft(1, vec![1], 10, 1, new_storage());
     r.add_node(2);
     assert_eq!(r.prs().nodes(), vec![1, 2]);
@@ -3181,6 +3254,7 @@ fn test_add_node() {
 
 #[test]
 fn test_add_node_check_quorum() {
+    let _ = env_logger::try_init();
     let mut r = new_test_raft(1, vec![1], 10, 1, new_storage());
     r.check_quorum = true;
 
@@ -3212,6 +3286,7 @@ fn test_add_node_check_quorum() {
 // and removed list correctly.
 #[test]
 fn test_remove_node() {
+    let _ = env_logger::try_init();
     let mut r = new_test_raft(1, vec![1, 2], 10, 1, new_storage());
     r.remove_node(2);
     assert_eq!(r.prs().nodes(), vec![1]);
@@ -3223,6 +3298,7 @@ fn test_remove_node() {
 
 #[test]
 fn test_promotable() {
+    let _ = env_logger::try_init();
     let id = 1u64;
     let mut tests = vec![
         (vec![1], true),
@@ -3240,6 +3316,7 @@ fn test_promotable() {
 
 #[test]
 fn test_raft_nodes() {
+    let _ = env_logger::try_init();
     let mut tests = vec![
         (vec![1, 2, 3], vec![1, 2, 3]),
         (vec![3, 2, 1], vec![1, 2, 3]),
@@ -3254,11 +3331,13 @@ fn test_raft_nodes() {
 
 #[test]
 fn test_campaign_while_leader() {
+    let _ = env_logger::try_init();
     test_campaign_while_leader_with_pre_vote(false);
 }
 
 #[test]
 fn test_pre_campaign_while_leader() {
+    let _ = env_logger::try_init();
     test_campaign_while_leader_with_pre_vote(true);
 }
 
@@ -3279,6 +3358,7 @@ fn test_campaign_while_leader_with_pre_vote(pre_vote: bool) {
 // committed when a config change reduces the quorum requirements.
 #[test]
 fn test_commit_after_remove_node() {
+    let _ = env_logger::try_init();
     // Create a cluster with two nodes.
     let s = new_storage();
     let mut r = new_test_raft(1, vec![1, 2], 5, 1, s.clone());
@@ -3329,6 +3409,7 @@ fn test_commit_after_remove_node() {
 // if the transferee has the most up-to-date log entries when transfer starts.
 #[test]
 fn test_leader_transfer_to_uptodate_node() {
+    let _ = env_logger::try_init();
     let mut nt = Network::new(vec![None, None, None]);
     nt.send(vec![new_message(1, 1, MessageType::MsgHup, 0)]);
 
@@ -3352,6 +3433,7 @@ fn test_leader_transfer_to_uptodate_node() {
 // to the follower.
 #[test]
 fn test_leader_transfer_to_uptodate_node_from_follower() {
+    let _ = env_logger::try_init();
     let mut nt = Network::new(vec![None, None, None]);
     nt.send(vec![new_message(1, 1, MessageType::MsgHup, 0)]);
 
@@ -3372,6 +3454,7 @@ fn test_leader_transfer_to_uptodate_node_from_follower() {
 // even the current leader is still under its leader lease
 #[test]
 fn test_leader_transfer_with_check_quorum() {
+    let _ = env_logger::try_init();
     let mut nt = Network::new(vec![None, None, None]);
     for i in 1..4 {
         let r = &mut nt.peers.get_mut(&i).unwrap();
@@ -3406,6 +3489,7 @@ fn test_leader_transfer_with_check_quorum() {
 
 #[test]
 fn test_leader_transfer_to_slow_follower() {
+    let _ = env_logger::try_init();
     let mut nt = Network::new(vec![None, None, None]);
     nt.send(vec![new_message(1, 1, MessageType::MsgHup, 0)]);
 
@@ -3423,6 +3507,7 @@ fn test_leader_transfer_to_slow_follower() {
 
 #[test]
 fn test_leader_transfer_after_snapshot() {
+    let _ = env_logger::try_init();
     let mut nt = Network::new(vec![None, None, None]);
     nt.send(vec![new_message(1, 1, MessageType::MsgHup, 0)]);
 
@@ -3459,6 +3544,7 @@ fn test_leader_transfer_after_snapshot() {
 
 #[test]
 fn test_leader_transfer_to_self() {
+    let _ = env_logger::try_init();
     let mut nt = Network::new(vec![None, None, None]);
     nt.send(vec![new_message(1, 1, MessageType::MsgHup, 0)]);
 
@@ -3469,6 +3555,7 @@ fn test_leader_transfer_to_self() {
 
 #[test]
 fn test_leader_transfer_to_non_existing_node() {
+    let _ = env_logger::try_init();
     let mut nt = Network::new(vec![None, None, None]);
     nt.send(vec![new_message(1, 1, MessageType::MsgHup, 0)]);
 
@@ -3479,6 +3566,7 @@ fn test_leader_transfer_to_non_existing_node() {
 
 #[test]
 fn test_leader_transfer_timeout() {
+    let _ = env_logger::try_init();
     let mut nt = Network::new(vec![None, None, None]);
     nt.send(vec![new_message(1, 1, MessageType::MsgHup, 0)]);
 
@@ -3502,6 +3590,7 @@ fn test_leader_transfer_timeout() {
 
 #[test]
 fn test_leader_transfer_ignore_proposal() {
+    let _ = env_logger::try_init();
     let mut nt = Network::new(vec![None, None, None]);
     nt.send(vec![new_message(1, 1, MessageType::MsgHup, 0)]);
 
@@ -3526,6 +3615,7 @@ fn test_leader_transfer_ignore_proposal() {
 
 #[test]
 fn test_leader_transfer_receive_higher_term_vote() {
+    let _ = env_logger::try_init();
     let mut nt = Network::new(vec![None, None, None]);
     nt.send(vec![new_message(1, 1, MessageType::MsgHup, 0)]);
 
@@ -3547,6 +3637,7 @@ fn test_leader_transfer_receive_higher_term_vote() {
 
 #[test]
 fn test_leader_transfer_remove_node() {
+    let _ = env_logger::try_init();
     let mut nt = Network::new(vec![None, None, None]);
     nt.send(vec![new_message(1, 1, MessageType::MsgHup, 0)]);
 
@@ -3565,6 +3656,7 @@ fn test_leader_transfer_remove_node() {
 // back to self when last transfer is pending.
 #[test]
 fn test_leader_transfer_back() {
+    let _ = env_logger::try_init();
     let mut nt = Network::new(vec![None, None, None]);
     nt.send(vec![new_message(1, 1, MessageType::MsgHup, 0)]);
 
@@ -3583,6 +3675,7 @@ fn test_leader_transfer_back() {
 // when last transfer is pending.
 #[test]
 fn test_leader_transfer_second_transfer_to_another_node() {
+    let _ = env_logger::try_init();
     let mut nt = Network::new(vec![None, None, None]);
     nt.send(vec![new_message(1, 1, MessageType::MsgHup, 0)]);
 
@@ -3601,6 +3694,7 @@ fn test_leader_transfer_second_transfer_to_another_node() {
 // to the same node should not extend the timeout while the first one is pending.
 #[test]
 fn test_leader_transfer_second_transfer_to_same_node() {
+    let _ = env_logger::try_init();
     let mut nt = Network::new(vec![None, None, None]);
     nt.send(vec![new_message(1, 1, MessageType::MsgHup, 0)]);
 
@@ -3641,6 +3735,7 @@ fn check_leader_transfer_state(r: &Raft<MemStorage>, state: StateRole, lead: u64
 // transitioned to StateRole::Leader)
 #[test]
 fn test_transfer_non_member() {
+    let _ = env_logger::try_init();
     let mut raft = new_test_raft(1, vec![2, 3, 4], 5, 1, new_storage());
     raft.step(new_message(2, 1, MessageType::MsgTimeoutNow, 0))
         .expect("");;
@@ -3659,6 +3754,7 @@ fn test_transfer_non_member() {
 // enabled.
 #[test]
 fn test_node_with_smaller_term_can_complete_election() {
+    let _ = env_logger::try_init();
     let mut n1 = new_test_raft_with_prevote(1, vec![1, 2, 3], 10, 1, new_storage(), true);
     let mut n2 = new_test_raft_with_prevote(2, vec![1, 2, 3], 10, 1, new_storage(), true);
     let mut n3 = new_test_raft_with_prevote(3, vec![1, 2, 3], 10, 1, new_storage(), true);
@@ -3732,6 +3828,7 @@ pub fn new_test_learner_raft(
 // even when times out.
 #[test]
 fn test_learner_election_timeout() {
+    let _ = env_logger::try_init();
     let mut n1 = new_test_learner_raft(1, vec![1], vec![2], 10, 1, new_storage());
     n1.become_follower(1, INVALID_ID);
 
@@ -3752,6 +3849,7 @@ fn test_learner_election_timeout() {
 // it is promoted to a normal peer.
 #[test]
 fn test_learner_promotion() {
+    let _ = env_logger::try_init();
     let mut n1 = new_test_learner_raft(1, vec![1], vec![2], 10, 1, new_storage());
     n1.become_follower(1, INVALID_ID);
 
@@ -3803,6 +3901,7 @@ fn test_learner_promotion() {
 // TestLearnerLogReplication tests that a learner can receive entries from the leader.
 #[test]
 fn test_learner_log_replication() {
+    let _ = env_logger::try_init();
     let n1 = new_test_learner_raft(1, vec![1], vec![2], 10, 1, new_storage());
     let n2 = new_test_learner_raft(2, vec![1], vec![2], 10, 1, new_storage());
     let mut network = Network::new(vec![Some(n1), Some(n2)]);
@@ -3858,6 +3957,7 @@ fn test_learner_log_replication() {
 // TestRestoreWithLearner restores a snapshot which contains learners.
 #[test]
 fn test_restore_with_learner() {
+    let _ = env_logger::try_init();
     let mut s = new_snapshot(11, 11, vec![1, 2]);
     s.mut_metadata().mut_conf_state().mut_learners().push(3);
 
@@ -3886,6 +3986,7 @@ fn test_restore_with_learner() {
 // when restores snapshot.
 #[test]
 fn test_restore_invalid_learner() {
+    let _ = env_logger::try_init();
     let mut s = new_snapshot(11, 11, vec![1, 2]);
     s.mut_metadata().mut_conf_state().mut_learners().push(3);
 
@@ -3898,6 +3999,7 @@ fn test_restore_invalid_learner() {
 // restoring snapshot.
 #[test]
 fn test_restore_learner_promotion() {
+    let _ = env_logger::try_init();
     let s = new_snapshot(11, 11, vec![1, 2, 3]);
     let mut sm = new_test_learner_raft(3, vec![1, 2], vec![3], 10, 1, new_storage());
     assert!(sm.is_learner);
@@ -3908,6 +4010,7 @@ fn test_restore_learner_promotion() {
 // TestLearnerReceiveSnapshot tests that a learner can receive a snpahost from leader.
 #[test]
 fn test_learner_receive_snapshot() {
+    let _ = env_logger::try_init();
     let mut s = new_snapshot(11, 11, vec![1]);
     s.mut_metadata().mut_conf_state().mut_learners().push(2);
 
@@ -3945,6 +4048,7 @@ fn test_learner_receive_snapshot() {
 // TestAddLearner tests that addLearner could update nodes correctly.
 #[test]
 fn test_add_learner() {
+    let _ = env_logger::try_init();
     let mut n1 = new_test_raft(1, vec![1], 10, 1, new_storage());
     n1.add_learner(2);
 
@@ -3956,6 +4060,7 @@ fn test_add_learner() {
 // and removed list correctly.
 #[test]
 fn test_remove_learner() {
+    let _ = env_logger::try_init();
     let mut n1 = new_test_learner_raft(1, vec![1], vec![2], 10, 1, new_storage());
     n1.remove_node(2);
     assert_eq!(n1.prs().nodes(), vec![1]);
@@ -4018,6 +4123,7 @@ fn new_prevote_migration_cluster() -> Network {
 
 #[test]
 fn test_prevote_migration_can_complete_election() {
+    let _ = env_logger::try_init();
     // n1 is leader with term 2
     // n2 is follower with term 2
     // n3 is pre-candidate with term 4, and less log
@@ -4047,6 +4153,7 @@ fn test_prevote_migration_can_complete_election() {
 
 #[test]
 fn test_prevote_migration_with_free_stuck_pre_candidate() {
+    let _ = env_logger::try_init();
     let mut nt = new_prevote_migration_cluster();
 
     // n1 is leader with term 2
@@ -4076,6 +4183,7 @@ fn test_prevote_migration_with_free_stuck_pre_candidate() {
 
 #[test]
 fn test_learner_respond_vote() {
+    let _ = env_logger::try_init();
     let mut n1 = new_test_learner_raft(1, vec![1, 2], vec![3], 10, 1, new_storage());
     n1.become_follower(1, INVALID_ID);
     n1.reset_randomized_election_timeout();
@@ -4104,6 +4212,7 @@ fn test_learner_respond_vote() {
 
 #[test]
 fn test_election_tick_range() {
+    let _ = env_logger::try_init();
     let mut cfg = new_test_config(1, vec![1, 2, 3], 10, 1);
     let mut raft = Raft::new(&cfg, new_storage());
     for _ in 0..1000 {
@@ -4139,6 +4248,7 @@ fn test_election_tick_range() {
 // election in next round.
 #[test]
 fn test_prevote_with_split_vote() {
+    let _ = env_logger::try_init();
     let peers = (1..=3).map(|id| {
         let mut raft = new_test_raft_with_prevote(id, vec![1, 2, 3], 10, 1, new_storage(), true);
         raft.become_follower(1, INVALID_ID);
@@ -4185,6 +4295,7 @@ fn test_prevote_with_split_vote() {
 // ensure that after a node become pre-candidate, it will checkQuorum correctly.
 #[test]
 fn test_prevote_with_check_quorum() {
+    let _ = env_logger::try_init();
     let bootstrap = |id| {
         let mut cfg = new_test_config(id, vec![1, 2, 3], 10, 1);
         cfg.pre_vote = true;
diff --git a/tests/cases/test_raft_flow_control.rs b/tests/cases/test_raft_flow_control.rs
index 316445a3d..f141ca2a1 100644
--- a/tests/cases/test_raft_flow_control.rs
+++ b/tests/cases/test_raft_flow_control.rs
@@ -27,12 +27,14 @@
 
 use super::test_raft::*;
 use raft::eraftpb::*;
+use env_logger;
 
 // test_msg_app_flow_control_full ensures:
 // 1. msgApp can fill the sending window until full
 // 2. when the window is full, no more msgApp can be sent.
 #[test]
 fn test_msg_app_flow_control_full() {
+    let _ = env_logger::try_init();
     let mut r = new_test_raft(1, vec![1, 2], 5, 1, new_storage());
     r.become_candidate();
     r.become_leader();
@@ -69,6 +71,7 @@ fn test_msg_app_flow_control_full() {
 // 2. out-of-dated msgAppResp has no effect on the sliding window.
 #[test]
 fn test_msg_app_flow_control_move_forward() {
+    let _ = env_logger::try_init();
     let mut r = new_test_raft(1, vec![1, 2], 5, 1, new_storage());
     r.become_candidate();
     r.become_leader();
@@ -122,6 +125,7 @@ fn test_msg_app_flow_control_move_forward() {
 // frees one slot if the window is full.
 #[test]
 fn test_msg_app_flow_control_recv_heartbeat() {
+    let _ = env_logger::try_init();
     let mut r = new_test_raft(1, vec![1, 2], 5, 1, new_storage());
     r.become_candidate();
     r.become_leader();
diff --git a/tests/cases/test_raft_paper.rs b/tests/cases/test_raft_paper.rs
index f8325b257..24d0887d3 100644
--- a/tests/cases/test_raft_paper.rs
+++ b/tests/cases/test_raft_paper.rs
@@ -30,6 +30,7 @@ use protobuf::RepeatedField;
 use raft::eraftpb::*;
 use raft::storage::MemStorage;
 use raft::*;
+use env_logger;
 
 pub fn hard_state(t: u64, c: u64, v: u64) -> HardState {
     let mut hs = HardState::new();
@@ -71,16 +72,19 @@ fn accept_and_reply(m: &Message) -> Message {
 
 #[test]
 fn test_follower_update_term_from_message() {
+    let _ = env_logger::try_init();
     test_update_term_from_message(StateRole::Follower);
 }
 
 #[test]
 fn test_candidate_update_term_from_message() {
+    let _ = env_logger::try_init();
     test_update_term_from_message(StateRole::Candidate);
 }
 
 #[test]
 fn test_leader_update_term_from_message() {
+    let _ = env_logger::try_init();
     test_update_term_from_message(StateRole::Leader);
 }
 
@@ -115,6 +119,7 @@ fn test_update_term_from_message(state: StateRole) {
 // Reference: section 5.1
 #[test]
 fn test_reject_stale_term_message() {
+    let _ = env_logger::try_init();
     let mut r = new_test_raft(1, vec![1, 2, 3], 10, 1, new_storage());
     let panic_before_step_state =
         Box::new(|_: &Message| panic!("before step state function hook called unexpectedly"));
@@ -130,6 +135,7 @@ fn test_reject_stale_term_message() {
 // Reference: section 5.2
 #[test]
 fn test_start_as_follower() {
+    let _ = env_logger::try_init();
     let r = new_test_raft(1, vec![1, 2, 3], 10, 1, new_storage());
     assert_eq!(r.state, StateRole::Follower);
 }
@@ -140,6 +146,7 @@ fn test_start_as_follower() {
 // Reference: section 5.2
 #[test]
 fn test_leader_bcast_beat() {
+    let _ = env_logger::try_init();
     // heartbeat interval
     let hi = 1;
     let mut r = new_test_raft(1, vec![1, 2, 3], 10, hi, new_storage());
@@ -169,11 +176,13 @@ fn test_leader_bcast_beat() {
 
 #[test]
 fn test_follower_start_election() {
+    let _ = env_logger::try_init();
     test_nonleader_start_election(StateRole::Follower);
 }
 
 #[test]
 fn test_candidate_start_new_election() {
+    let _ = env_logger::try_init();
     test_nonleader_start_election(StateRole::Candidate);
 }
 
@@ -225,6 +234,7 @@ fn test_nonleader_start_election(state: StateRole) {
 // Reference: section 5.2
 #[test]
 fn test_leader_election_in_one_round_rpc() {
+    let _ = env_logger::try_init();
     let mut tests = vec![
         // win the election when receiving votes from a majority of the servers
         (1, map!(), StateRole::Leader),
@@ -281,6 +291,7 @@ fn test_leader_election_in_one_round_rpc() {
 // Reference: section 5.2
 #[test]
 fn test_follower_vote() {
+    let _ = env_logger::try_init();
     let mut tests = vec![
         (INVALID_ID, 1, false),
         (INVALID_ID, 2, false),
@@ -316,6 +327,7 @@ fn test_follower_vote() {
 // Reference: section 5.2
 #[test]
 fn test_candidate_fallback() {
+    let _ = env_logger::try_init();
     let new_message_ext = |f, to, term| {
         let mut m = new_message(f, to, MessageType::MsgAppend, 0);
         m.set_term(term);
@@ -346,11 +358,13 @@ fn test_candidate_fallback() {
 
 #[test]
 fn test_follower_election_timeout_randomized() {
+    let _ = env_logger::try_init();
     test_non_leader_election_timeout_randomized(StateRole::Follower);
 }
 
 #[test]
 fn test_candidate_election_timeout_randomized() {
+    let _ = env_logger::try_init();
     test_non_leader_election_timeout_randomized(StateRole::Candidate);
 }
 
@@ -385,11 +399,13 @@ fn test_non_leader_election_timeout_randomized(state: StateRole) {
 
 #[test]
 fn test_follower_election_timeout_nonconflict() {
+    let _ = env_logger::try_init();
     test_nonleaders_election_timeout_nonconfict(StateRole::Follower);
 }
 
 #[test]
 fn test_acandidates_election_timeout_nonconf() {
+    let _ = env_logger::try_init();
     test_nonleaders_election_timeout_nonconfict(StateRole::Candidate);
 }
 
@@ -444,6 +460,7 @@ fn test_nonleaders_election_timeout_nonconfict(state: StateRole) {
 // Reference: section 5.3
 #[test]
 fn test_leader_start_replication() {
+    let _ = env_logger::try_init();
     let s = new_storage();
     let mut r = new_test_raft(1, vec![1, 2, 3], 10, 1, s.clone());
     r.become_candidate();
@@ -485,6 +502,7 @@ fn test_leader_start_replication() {
 // Reference: section 5.3
 #[test]
 fn test_leader_commit_entry() {
+    let _ = env_logger::try_init();
     let s = new_storage();
     let mut r = new_test_raft(1, vec![1, 2, 3], 10, 1, s.clone());
     r.become_candidate();
@@ -515,6 +533,7 @@ fn test_leader_commit_entry() {
 // Reference: section 5.3
 #[test]
 fn test_leader_acknowledge_commit() {
+    let _ = env_logger::try_init();
     let mut tests = vec![
         (1, map!(), true),
         (3, map!(), false),
@@ -556,6 +575,7 @@ fn test_leader_acknowledge_commit() {
 // Reference: section 5.3
 #[test]
 fn test_leader_commit_preceding_entries() {
+    let _ = env_logger::try_init();
     let mut tests = vec![
         vec![],
         vec![empty_entry(2, 1)],
@@ -595,6 +615,7 @@ fn test_leader_commit_preceding_entries() {
 // Reference: section 5.3
 #[test]
 fn test_follower_commit_entry() {
+    let _ = env_logger::try_init();
     let mut tests = vec![
         (vec![new_entry(1, 1, SOME_DATA)], 1),
         (
@@ -651,6 +672,7 @@ fn test_follower_commit_entry() {
 // Reference: section 5.3
 #[test]
 fn test_follower_check_msg_append() {
+    let _ = env_logger::try_init();
     let ents = vec![empty_entry(1, 1), empty_entry(2, 2)];
     let mut tests = vec![
         // match with committed entries
@@ -710,6 +732,7 @@ fn test_follower_check_msg_append() {
 // Reference: section 5.3
 #[test]
 fn test_follower_append_entries() {
+    let _ = env_logger::try_init();
     let mut tests = vec![
         (
             2,
@@ -776,6 +799,7 @@ fn test_follower_append_entries() {
 // Reference: section 5.3, figure 7
 #[test]
 fn test_leader_sync_follower_log() {
+    let _ = env_logger::try_init();
     let ents = vec![
         empty_entry(0, 0),
         empty_entry(1, 1),
@@ -904,6 +928,7 @@ fn test_leader_sync_follower_log() {
 // Reference: section 5.4.1
 #[test]
 fn test_vote_request() {
+    let _ = env_logger::try_init();
     let mut tests = vec![
         (vec![empty_entry(1, 1)], 2),
         (vec![empty_entry(1, 1), empty_entry(2, 2)], 3),
@@ -966,6 +991,7 @@ fn test_vote_request() {
 // Reference: section 5.4.1
 #[test]
 fn test_voter() {
+    let _ = env_logger::try_init();
     let mut tests = vec![
         // same logterm
         (vec![empty_entry(1, 1)], 1, 1, false),
@@ -1019,6 +1045,7 @@ fn test_voter() {
 // Reference: section 5.4.2
 #[test]
 fn test_leader_only_commits_log_from_current_term() {
+    let _ = env_logger::try_init();
     let ents = vec![empty_entry(1, 1), empty_entry(2, 2)];
     let mut tests = vec![
         // do not commit log entries in previous terms
diff --git a/tests/cases/test_raft_snap.rs b/tests/cases/test_raft_snap.rs
index bcc5a947b..a3064d281 100644
--- a/tests/cases/test_raft_snap.rs
+++ b/tests/cases/test_raft_snap.rs
@@ -27,6 +27,7 @@
 
 use super::test_raft::*;
 use raft::eraftpb::*;
+use env_logger;
 
 fn testing_snap() -> Snapshot {
     new_snapshot(11, 11, vec![1, 2])
@@ -34,6 +35,7 @@ fn testing_snap() -> Snapshot {
 
 #[test]
 fn test_sending_snapshot_set_pending_snapshot() {
+    let _ = env_logger::try_init();
     let mut sm = new_test_raft(1, vec![1], 10, 1, new_storage());
     sm.restore(testing_snap());
 
@@ -53,6 +55,7 @@ fn test_sending_snapshot_set_pending_snapshot() {
 
 #[test]
 fn test_pending_snapshot_pause_replication() {
+    let _ = env_logger::try_init();
     let mut sm = new_test_raft(1, vec![1, 2], 10, 1, new_storage());
     sm.restore(testing_snap());
 
@@ -68,6 +71,7 @@ fn test_pending_snapshot_pause_replication() {
 
 #[test]
 fn test_snapshot_failure() {
+    let _ = env_logger::try_init();
     let mut sm = new_test_raft(1, vec![1, 2], 10, 1, new_storage());
     sm.restore(testing_snap());
 
@@ -87,6 +91,7 @@ fn test_snapshot_failure() {
 
 #[test]
 fn test_snapshot_succeed() {
+    let _ = env_logger::try_init();
     let mut sm = new_test_raft(1, vec![1, 2], 10, 1, new_storage());
     sm.restore(testing_snap());
 
@@ -106,6 +111,7 @@ fn test_snapshot_succeed() {
 
 #[test]
 fn test_snapshot_abort() {
+    let _ = env_logger::try_init();
     let mut sm = new_test_raft(1, vec![1, 2], 10, 1, new_storage());
     sm.restore(testing_snap());
 
diff --git a/tests/cases/test_raw_node.rs b/tests/cases/test_raw_node.rs
index c74083b2f..751d6e643 100644
--- a/tests/cases/test_raw_node.rs
+++ b/tests/cases/test_raw_node.rs
@@ -32,6 +32,7 @@ use raft::eraftpb::*;
 use raft::storage::MemStorage;
 use raft::*;
 use std::sync::*;
+use env_logger;
 
 fn new_peer(id: u64) -> Peer {
     Peer {
@@ -93,6 +94,7 @@ fn new_raw_node(
 // test_raw_node_step ensures that RawNode.Step ignore local message.
 #[test]
 fn test_raw_node_step() {
+    let _ = env_logger::try_init();
     for msg_t in MessageType::values() {
         let mut raw_node = new_raw_node(1, vec![], 10, 1, new_storage(), vec![new_peer(1)]);
         let res = raw_node.step(new_message(0, 0, *msg_t, 0));
@@ -113,6 +115,7 @@ fn test_raw_node_step() {
 // forward to the new leader and 'send' method does not attach its term
 #[test]
 fn test_raw_node_read_index_to_old_leader() {
+    let _ = env_logger::try_init();
     let r1 = new_test_raft(1, vec![1, 2, 3], 10, 1, new_storage());
     let r2 = new_test_raft(2, vec![1, 2, 3], 10, 1, new_storage());
     let r3 = new_test_raft(3, vec![1, 2, 3], 10, 1, new_storage());
@@ -174,6 +177,7 @@ fn test_raw_node_read_index_to_old_leader() {
 // RawNode.propose_conf_change send the given proposal and ConfChange to the underlying raft.
 #[test]
 fn test_raw_node_propose_and_conf_change() {
+    let _ = env_logger::try_init();
     let s = new_storage();
     let mut raw_node = new_raw_node(1, vec![], 10, 1, s.clone(), vec![new_peer(1)]);
     let rd = raw_node.ready();
@@ -217,6 +221,7 @@ fn test_raw_node_propose_and_conf_change() {
 // not affect the later propose to add new node.
 #[test]
 fn test_raw_node_propose_add_duplicate_node() {
+    let _ = env_logger::try_init();
     let s = new_storage();
     let mut raw_node = new_raw_node(1, vec![], 10, 1, s.clone(), vec![new_peer(1)]);
     let rd = raw_node.ready();
@@ -270,6 +275,7 @@ fn test_raw_node_propose_add_duplicate_node() {
 
 #[test]
 fn test_raw_node_propose_add_learner_node() {
+    let _ = env_logger::try_init();
     let s = new_storage();
     let mut raw_node = new_raw_node(1, vec![], 10, 1, s.clone(), vec![new_peer(1)]);
     let rd = raw_node.ready();
@@ -310,6 +316,7 @@ fn test_raw_node_propose_add_learner_node() {
 // to the underlying raft. It also ensures that ReadState can be read out.
 #[test]
 fn test_raw_node_read_index() {
+    let _ = env_logger::try_init();
     let a = Arc::new(RwLock::new(Vec::new()));
     let b = Arc::clone(&a);
     let before_step_state = Box::new(move |m: &Message| {
@@ -364,6 +371,7 @@ fn test_raw_node_read_index() {
 // proposals.
 #[test]
 fn test_raw_node_start() {
+    let _ = env_logger::try_init();
     let cc = conf_change(ConfChangeType::AddNode, 1);
     let ccdata = protobuf::Message::write_to_bytes(&cc).unwrap();
     let wants = vec![
@@ -420,6 +428,7 @@ fn test_raw_node_start() {
 
 #[test]
 fn test_raw_node_restart() {
+    let _ = env_logger::try_init();
     let entries = vec![empty_entry(1, 1), new_entry(1, 2, Some("foo"))];
     let st = hard_state(1, 1, 0);
 
@@ -437,6 +446,7 @@ fn test_raw_node_restart() {
 
 #[test]
 fn test_raw_node_restart_from_snapshot() {
+    let _ = env_logger::try_init();
     let snap = new_snapshot(2, 1, vec![1, 2]);
     let entries = vec![new_entry(1, 3, Some("foo"))];
     let st = hard_state(1, 3, 0);
@@ -458,6 +468,7 @@ fn test_raw_node_restart_from_snapshot() {
 // when skip_bcast_commit is true.
 #[test]
 fn test_skip_bcast_commit() {
+    let _ = env_logger::try_init();
     let mut config = new_test_config(1, vec![1, 2, 3], 10, 1);
     config.skip_bcast_commit = true;
     let r1 = new_test_raft_with_config(&config, new_storage());
diff --git a/tests/tests.rs b/tests/tests.rs
index 47d427152..d14491709 100644
--- a/tests/tests.rs
+++ b/tests/tests.rs
@@ -20,6 +20,7 @@ extern crate log;
 extern crate protobuf;
 extern crate raft;
 extern crate rand;
+extern crate env_logger;
 
 /// Get the count of macro's arguments.
 ///