diff --git a/test_runner/batch_others/test_branch_behind.py b/test_runner/batch_others/test_branch_behind.py
index ca3a90205b..dedcf7f63c 100644
--- a/test_runner/batch_others/test_branch_behind.py
+++ b/test_runner/batch_others/test_branch_behind.py
@@ -30,7 +30,7 @@ def test_branch_behind(zenith_cli, pageserver: ZenithPageserver, postgres: Postg
     ''')
     main_cur.execute('SELECT pg_current_wal_insert_lsn()')
     lsn_a = main_cur.fetchone()[0]
-    log.info('LSN after 100 rows: ' + lsn_a)
+    log.info(f'LSN after 100 rows: {lsn_a}')
 
     # Insert some more rows. (This generates enough WAL to fill a few segments.)
     main_cur.execute('''
@@ -40,7 +40,7 @@ def test_branch_behind(zenith_cli, pageserver: ZenithPageserver, postgres: Postg
     ''')
     main_cur.execute('SELECT pg_current_wal_insert_lsn()')
     lsn_b = main_cur.fetchone()[0]
-    log.info('LSN after 100100 rows: ' + lsn_b)
+    log.info(f'LSN after 100100 rows: {lsn_b}')
 
     # Branch at the point where only 100 rows were inserted
     zenith_cli.run(["branch", "test_branch_behind_hundred", "test_branch_behind@" + lsn_a])
@@ -55,7 +55,7 @@ def test_branch_behind(zenith_cli, pageserver: ZenithPageserver, postgres: Postg
 
     main_cur.execute('SELECT pg_current_wal_insert_lsn()')
     lsn_c = main_cur.fetchone()[0]
-    log.info('LSN after 200100 rows: ' + lsn_c)
+    log.info(f'LSN after 200100 rows: {lsn_c}')
 
     # Branch at the point where only 200 rows were inserted
     zenith_cli.run(["branch", "test_branch_behind_more", "test_branch_behind@" + lsn_b])
diff --git a/test_runner/batch_others/test_clog_truncate.py b/test_runner/batch_others/test_clog_truncate.py
index d7cc1c502b..7061939fd9 100644
--- a/test_runner/batch_others/test_clog_truncate.py
+++ b/test_runner/batch_others/test_clog_truncate.py
@@ -49,10 +49,10 @@ def test_clog_truncate(zenith_cli, pageserver: ZenithPageserver, postgres: Postg
     # wait for autovacuum to truncate the pg_xact
     # XXX Is it worth to add a timeout here?
     pg_xact_0000_path = os.path.join(pg.pg_xact_dir_path(), '0000')
-    log.info("pg_xact_0000_path = " + pg_xact_0000_path)
+    log.info(f"pg_xact_0000_path = {pg_xact_0000_path}")
 
     while os.path.isfile(pg_xact_0000_path):
-        log.info("file exists. wait for truncation. " "pg_xact_0000_path = " + pg_xact_0000_path)
+        log.info(f"file exists. wait for truncation. " "pg_xact_0000_path = {pg_xact_0000_path}")
         time.sleep(5)
 
     # checkpoint to advance latest lsn
@@ -63,7 +63,7 @@ def test_clog_truncate(zenith_cli, pageserver: ZenithPageserver, postgres: Postg
             lsn_after_truncation = cur.fetchone()[0]
 
     # create new branch after clog truncation and start a compute node on it
-    log.info('create branch at lsn_after_truncation ' + lsn_after_truncation)
+    log.info(f'create branch at lsn_after_truncation {lsn_after_truncation}')
     zenith_cli.run(
         ["branch", "test_clog_truncate_new", "test_clog_truncate@" + lsn_after_truncation])
 
diff --git a/test_runner/batch_others/test_restart_compute.py b/test_runner/batch_others/test_restart_compute.py
index 624ea53d21..0504930674 100644
--- a/test_runner/batch_others/test_restart_compute.py
+++ b/test_runner/batch_others/test_restart_compute.py
@@ -43,7 +43,7 @@ def test_restart_compute(
             cur.execute('SELECT sum(key) FROM t')
             r = cur.fetchone()
             assert r == (5000050000, )
-            log.info("res = " + r)
+            log.info(f"res = {r}")
 
     # Remove data directory and restart
     pg.stop_and_destroy().create_start('test_restart_compute',
@@ -56,7 +56,7 @@ def test_restart_compute(
             cur.execute('SELECT sum(key) FROM t')
             r = cur.fetchone()
             assert r == (5000050000, )
-            log.info("res = " + r)
+            log.info(f"res = {r}")
 
             # Insert another row
             cur.execute("INSERT INTO t VALUES (100001, 'payload2')")
@@ -64,7 +64,7 @@ def test_restart_compute(
 
             r = cur.fetchone()
             assert r == (100001, )
-            log.info("res = " + r)
+            log.info(f"res = {r}")
 
     # Again remove data directory and restart
     pg.stop_and_destroy().create_start('test_restart_compute',
@@ -79,7 +79,7 @@ def test_restart_compute(
 
             r = cur.fetchone()
             assert r == (100001, )
-            log.info("res = " + r)
+            log.info(f"res = {r}")
 
     # And again remove data directory and restart
     pg.stop_and_destroy().create_start('test_restart_compute',
@@ -92,4 +92,4 @@ def test_restart_compute(
 
             r = cur.fetchone()
             assert r == (100001, )
-            log.info("res = " + r)
+            log.info(f"res = {r}")
diff --git a/test_runner/fixtures/zenith_fixtures.py b/test_runner/fixtures/zenith_fixtures.py
index 198b51f436..ac32524323 100644
--- a/test_runner/fixtures/zenith_fixtures.py
+++ b/test_runner/fixtures/zenith_fixtures.py
@@ -948,7 +948,7 @@ def base_dir() -> str:
     """ find the base directory (currently this is the git root) """
 
     base_dir = os.path.normpath(os.path.join(get_self_dir(), '../..'))
-    log.info('\nbase_dir is ' + base_dir)
+    log.info(f'base_dir is {base_dir}')
     return base_dir
 
 
@@ -977,7 +977,7 @@ def test_output_dir(request: Any, top_output_dir: str) -> str:
         test_name = 'shared'
 
     test_output_dir = os.path.join(top_output_dir, test_name)
-    log.info('test_output_dir is ' + test_output_dir)
+    log.info(f'test_output_dir is {test_output_dir}')
     shutil.rmtree(test_output_dir, ignore_errors=True)
     mkdir_if_needed(test_output_dir)
     return test_output_dir
@@ -1019,7 +1019,7 @@ def pg_distrib_dir(base_dir: str) -> str:
         pg_dir = env_postgres_bin
     else:
         pg_dir = os.path.normpath(os.path.join(base_dir, DEFAULT_POSTGRES_DIR))
-    log.info('postgres dir is ' + pg_dir)
+    log.info(f'postgres dir is {pg_dir}')
     if not os.path.exists(os.path.join(pg_dir, 'bin/postgres')):
         raise Exception('postgres not found at "{}"'.format(pg_dir))
     return pg_dir