diff --git a/tests/test_checksum.py b/tests/test_checksum.py
index 0f71e4c60500b2eca6301305fc57654d23f418c8..add5e74e967afa52d957c6b37e8f884eb0fed087 100644
--- a/tests/test_checksum.py
+++ b/tests/test_checksum.py
@@ -21,7 +21,7 @@ from silkaj.cli import cli
 
 pubkey = "3rp7ahDGeXqffBQTnENiXEFXYS7BRjYmS33NbgfCuDc8"
 checksum = "DFQ"
-pubkey_checksum = pubkey + ":" + checksum
+pubkey_checksum = f"{pubkey}:{checksum}"
 pubkey_seedhex_authfile = (
     "3bc6f2484e441e40562155235cdbd8ce04c25e7df35bf5f87c067bf239db8511"
 )
@@ -31,7 +31,7 @@ pubkey_seedhex_authfile = (
     "command, excepted_output",
     [
         (["checksum", pubkey_checksum], "The checksum is valid"),
-        (["checksum", pubkey + ":vAK"], "The checksum is invalid"),
+        (["checksum", f"{pubkey}:vAK"], "The checksum is invalid"),
         (["checksum", pubkey], pubkey_checksum),
         (["checksum", "uid"], "Error: Wrong public key format"),
         (["checksum"], MESSAGE),
@@ -44,4 +44,4 @@ def test_checksum_command(command, excepted_output):
         with open("authfile", "w") as f:
             f.write(pubkey_seedhex_authfile)
         result = CliRunner().invoke(cli, args=command)
-        assert result.output == excepted_output + "\n"
+        assert result.output == f"{excepted_output}\n"
diff --git a/tests/test_crypto_tools.py b/tests/test_crypto_tools.py
index e2247f5d6d50863ca8403bbc42a09b9740bb572c..299175bd3599119539a165361662773bbf5b2d63 100644
--- a/tests/test_crypto_tools.py
+++ b/tests/test_crypto_tools.py
@@ -42,7 +42,7 @@ def test_gen_checksum(pubkey, checksum):
     ],
 )
 def test_validate_checksum(pubkey, checksum, expected, capsys):
-    pubkey_with_ck = str(pubkey + ":" + checksum)
+    pubkey_with_ck = f"{pubkey}:{checksum}"
     if expected == None:
         assert pubkey == crypto_tools.validate_checksum(pubkey_with_ck)
     else:
diff --git a/tests/test_tui.py b/tests/test_tui.py
index 972bfa602b4918abeb69b2747e55af7a2edbf4b4..9ac6faaa7881404ccd70101195d0523475224f69 100644
--- a/tests/test_tui.py
+++ b/tests/test_tui.py
@@ -30,14 +30,8 @@ def test_display_amount(message, amount, currency_symbol):
     amount_UD = round(amount / mock_ud_value, 2)
     expected = [
         [
-            message + " (unit|relative)",
-            str(amount / 100)
-            + " "
-            + currency_symbol
-            + " | "
-            + str(amount_UD)
-            + " UD "
-            + currency_symbol,
+            f"{message} (unit|relative)",
+            f"{str(amount / 100)} {currency_symbol} | {str(amount_UD)} UD {currency_symbol}",
         ]
     ]
     tx = list()
@@ -56,9 +50,9 @@ def test_display_amount(message, amount, currency_symbol):
 def test_display_pubkey(message, pubkey, id, monkeypatch):
     monkeypatch.setattr(wot_tools, "is_member", patched_is_member)
 
-    expected = [[message + " (pubkey:checksum)", display_pubkey_and_checksum(pubkey)]]
+    expected = [[f"{message} (pubkey:checksum)", display_pubkey_and_checksum(pubkey)]]
     if id:
-        expected.append([message + " (id)", id])
+        expected.append([f"{message} (id)", id])
     tx = list()
     display_pubkey(tx, message, pubkey)
     assert tx == expected
diff --git a/tests/test_verify_blocks.py b/tests/test_verify_blocks.py
index af48140db616c1cff8937da19f688fe3f7ab1e89..16396ca3b4daa62ca8682dcc42040cd28eed6cc2 100644
--- a/tests/test_verify_blocks.py
+++ b/tests/test_verify_blocks.py
@@ -55,8 +55,8 @@ def test_check_passed_blocks_range(from_block, to_block, capsys, monkeypatch):
     assert pytest_wrapped_e.value.code == FAILURE_EXIT_STATUS
     captured = capsys.readouterr()
     if to_block == HEAD_BLOCK + 1:
-        expected = "Passed TO_BLOCK argument is bigger than the head block: " + str(
-            HEAD_BLOCK
+        expected = (
+            f"Passed TO_BLOCK argument is bigger than the head block: {str(HEAD_BLOCK)}"
         )
     else:
         expected = "TO_BLOCK should be bigger or equal to FROM_BLOCK\n"