diff --git a/tests/bugfixes/github/test_CVE_2017_1000126.py b/tests/bugfixes/github/test_CVE_2017_1000126.py
index d90530750f..9cfa17a5c2 100644
--- a/tests/bugfixes/github/test_CVE_2017_1000126.py
+++ b/tests/bugfixes/github/test_CVE_2017_1000126.py
@@ -7,7 +7,7 @@ class TestCvePoC(metaclass=system_tests.CaseMeta):
     url = "https://github.com/Exiv2/exiv2/issues/175"
 
     filename = "$data_path/cve_2017_1000126_stack-oob-read.webp"
-    commands = ["$exiv2 " + filename]
+    commands = [f"$exiv2 {filename}"]
     stdout = [""]
     stderr = [
         f"""$exiv2_exception_message {filename}:
diff --git a/tests/bugfixes/github/test_CVE_2017_14859.py b/tests/bugfixes/github/test_CVE_2017_14859.py
index 78f47934dd..2de675461b 100644
--- a/tests/bugfixes/github/test_CVE_2017_14859.py
+++ b/tests/bugfixes/github/test_CVE_2017_14859.py
@@ -10,15 +10,13 @@ class TestCvePoC(metaclass=system_tests.CaseMeta):
     commands = [f"$exiv2 {filename}"]
     stdout = [""]
     stderr = [
-        """$exiv2_exception_message """
-        + filename
-        + ":\n"
-        + (
-            "$kerFailedToReadImageData"
-            if system_tests.BT.Config.is_64bit
-            else "$kerCorruptedMetadata"
-        )
-        + "\n"
+        f"""$exiv2_exception_message {filename}:
+{(
+    "$kerFailedToReadImageData"
+    if system_tests.BT.Config.is_64bit
+    else "$kerCorruptedMetadata"
+)}
+"""
     ]
     retval = [1]
 
diff --git a/tests/bugfixes/github/test_CVE_2017_14860.py b/tests/bugfixes/github/test_CVE_2017_14860.py
index 90876de208..8c284f2d31 100644
--- a/tests/bugfixes/github/test_CVE_2017_14860.py
+++ b/tests/bugfixes/github/test_CVE_2017_14860.py
@@ -7,12 +7,10 @@ class TestCvePoC(metaclass=system_tests.CaseMeta):
     url = "https://github.com/Exiv2/exiv2/issues/73"
 
     filename = "$data_path/003-heap-buffer-over"
-    commands = ["$exiv2 " + filename]
+    commands = [f"$exiv2 {filename}"]
     stdout = [""]
     stderr = [
-        """$exiv2_exception_message """
-        + filename
-        + """:
+        f"""$exiv2_exception_message {filename}:
 $kerCorruptedMetadata
 """
     ]
diff --git a/tests/bugfixes/github/test_CVE_2017_14862.py b/tests/bugfixes/github/test_CVE_2017_14862.py
index 07328fe9bd..490641c410 100644
--- a/tests/bugfixes/github/test_CVE_2017_14862.py
+++ b/tests/bugfixes/github/test_CVE_2017_14862.py
@@ -8,16 +8,14 @@ class TestCvePoC(metaclass=system_tests.CaseMeta):
     url = "https://github.com/Exiv2/exiv2/issues/75"
 
     filename = "$data_path/008-invalid-mem"
-    commands = ["$exiv2 -q " + filename]
+    commands = [f"$exiv2 -q {filename}"]
 
     if system_tests.BT.Config.is_64bit:
         stderr = [""]
         retval = [0]
     else:
         stderr = [
-            """$exiv2_exception_message """
-            + filename
-            + """:
+            f"""$exiv2_exception_message {filename}:
 $kerCorruptedMetadata
 """
         ]
diff --git a/tests/bugfixes/github/test_CVE_2017_14864.py b/tests/bugfixes/github/test_CVE_2017_14864.py
index 7e27582f20..a17f853707 100644
--- a/tests/bugfixes/github/test_CVE_2017_14864.py
+++ b/tests/bugfixes/github/test_CVE_2017_14864.py
@@ -10,14 +10,12 @@ class TestCvePoC(metaclass=system_tests.CaseMeta):
     commands = [f"$exiv2 -q {filename}"]
     stdout = [""]
     stderr = [
-        """$exiv2_exception_message """
-        + filename
-        + ":\n"
-        + (
-            "$kerFailedToReadImageData"
-            if system_tests.BT.Config.is_64bit
-            else "$kerCorruptedMetadata"
-        )
-        + "\n"
+        f"""$exiv2_exception_message {filename}:
+{(
+    "$kerFailedToReadImageData"
+    if system_tests.BT.Config.is_64bit
+    else "$kerCorruptedMetadata"
+)}
+"""
     ]
     retval = [1]
diff --git a/tests/bugfixes/github/test_CVE_2017_17669.py b/tests/bugfixes/github/test_CVE_2017_17669.py
index 060fc7c98e..ba396d63d1 100644
--- a/tests/bugfixes/github/test_CVE_2017_17669.py
+++ b/tests/bugfixes/github/test_CVE_2017_17669.py
@@ -7,13 +7,11 @@ class TestCvePoC(metaclass=system_tests.CaseMeta):
     url = "https://github.com/Exiv2/exiv2/issues/187"
 
     filename = "$data_path/issue_187"
-    commands = ["$exiv2 " + filename]
+    commands = [f"$exiv2 {filename}"]
     retval = [1]
     stdout = [""]
     stderr = [
-        """$exiv2_exception_message """
-        + filename
-        + """:
+        f"""$exiv2_exception_message {filename}:
 $kerFailedToReadImageData
 """
     ]
diff --git a/tests/bugfixes/github/test_CVE_2017_17722.py b/tests/bugfixes/github/test_CVE_2017_17722.py
index fd9f795c29..1180678d74 100644
--- a/tests/bugfixes/github/test_CVE_2017_17722.py
+++ b/tests/bugfixes/github/test_CVE_2017_17722.py
@@ -7,13 +7,11 @@ class TestCvePoC(metaclass=system_tests.CaseMeta):
     url = "https://github.com/Exiv2/exiv2/issues/208"
 
     filename = "$data_path/2018-01-09-exiv2-crash-001.tiff"
-    commands = ["$exiv2 " + filename]
+    commands = [f"$exiv2 {filename}"]
     retval = [1]
     stdout = [""]
     stderr = [
-        """$exiv2_exception_message """
-        + filename
-        + """:
-$filename: $kerFileContainsUnknownImageType
+        f"""$exiv2_exception_message {filename}:
+{filename}: $kerFileContainsUnknownImageType
 """
     ]
diff --git a/tests/bugfixes/github/test_CVE_2017_17725.py b/tests/bugfixes/github/test_CVE_2017_17725.py
index 95631afbe8..72c2b861e8 100644
--- a/tests/bugfixes/github/test_CVE_2017_17725.py
+++ b/tests/bugfixes/github/test_CVE_2017_17725.py
@@ -8,12 +8,10 @@ class TestCvePoC(metaclass=system_tests.CaseMeta):
     found_by = ["Wei You", "@youwei1988"]
 
     filename = "$data_path/poc_2017-12-12_issue188"
-    commands = ["$exiv2 " + filename]
+    commands = [f"$exiv2 {filename}"]
     stdout = [""]
     stderr = [
-        """$exiv2_exception_message """
-        + filename
-        + """:
+        f"""$exiv2_exception_message {filename}:
 $kerCorruptedMetadata
 """
     ]
diff --git a/tests/bugfixes/github/test_CVE_2017_18005.py b/tests/bugfixes/github/test_CVE_2017_18005.py
index 88ec6f90be..a716880de5 100644
--- a/tests/bugfixes/github/test_CVE_2017_18005.py
+++ b/tests/bugfixes/github/test_CVE_2017_18005.py
@@ -20,9 +20,7 @@ class TestPoC(metaclass=system_tests.CaseMeta):
     commands = [f"$exiv2 -vPEIXxgklnycsvth -b {filename}"]
 
     stdout = [
-        """File 1/1: """
-        + filename
-        + """
+        f"""File 1/1: {filename}
 0x0117 Image        Exif.Image.StripByteCounts                   StripByteCounts             Strip Byte Count               SByte       0   0  
 
 """
diff --git a/tests/bugfixes/github/test_CVE_2018_10999.py b/tests/bugfixes/github/test_CVE_2018_10999.py
index d89988a0b4..99c1bda7ec 100644
--- a/tests/bugfixes/github/test_CVE_2018_10999.py
+++ b/tests/bugfixes/github/test_CVE_2018_10999.py
@@ -7,13 +7,11 @@ class TestCvePoC(metaclass=system_tests.CaseMeta):
     url = "https://github.com/Exiv2/exiv2/issues/306"
 
     filename = "$data_path/pocIssue306"
-    commands = ["$exiv2 -et " + filename]
+    commands = [f"$exiv2 -et {filename}"]
     retval = [1]
     stdout = [""]
     stderr = [
-        """$exception_in_extract """
-        + filename
-        + """:
+        f"""$exception_in_extract {filename}:
 $kerCorruptedMetadata
 """
     ]
diff --git a/tests/bugfixes/github/test_CVE_2018_4868.py b/tests/bugfixes/github/test_CVE_2018_4868.py
index 6f11cabbe0..cf1534c87b 100644
--- a/tests/bugfixes/github/test_CVE_2018_4868.py
+++ b/tests/bugfixes/github/test_CVE_2018_4868.py
@@ -9,12 +9,10 @@ class TestCvePoC(metaclass=system_tests.CaseMeta):
     found_by = ["afl", "topsecLab", "xcainiao"]
 
     filename = "$data_path/exiv2-memorymmap-error"
-    commands = ["$exiv2 " + filename]
+    commands = [f"$exiv2 {filename}"]
     stdout = [""]
     stderr = [
-        """$exiv2_exception_message """
-        + filename
-        + """:
+        f"""$exiv2_exception_message {filename}:
 $kerCorruptedMetadata
 """
     ]
diff --git a/tests/bugfixes/github/test_issue_1011.py b/tests/bugfixes/github/test_issue_1011.py
index 6cf2635020..3285732794 100644
--- a/tests/bugfixes/github/test_issue_1011.py
+++ b/tests/bugfixes/github/test_issue_1011.py
@@ -5,12 +5,10 @@
 
 class Test_issue_1011(metaclass=CaseMeta):
     filename = path("$data_path/Jp2Image_readMetadata_loop.poc")
-    commands = ["$exiv2 " + filename]
+    commands = [f"$exiv2 {filename}"]
     stdout = [""]
     stderr = [
-        """$exiv2_exception_message """
-        + filename
-        + """:
+        f"""$exiv2_exception_message {filename}:
 $kerCorruptedMetadata
 """
     ]
diff --git a/tests/bugfixes/github/test_issue_170.py b/tests/bugfixes/github/test_issue_170.py
index 324ac3d28f..74c3ca24c4 100644
--- a/tests/bugfixes/github/test_issue_170.py
+++ b/tests/bugfixes/github/test_issue_170.py
@@ -8,12 +8,10 @@ class DecodeIHDRChunkOutOfBoundsRead(metaclass=system_tests.CaseMeta):
 
     filename = "$data_path/issue_170_poc"
 
-    commands = ["$exiv2 " + filename]
+    commands = [f"$exiv2 {filename}"]
     stdout = [""]
     stderr = [
-        """$exiv2_exception_message """
-        + filename
-        + """:
+        f"""$exiv2_exception_message {filename}:
 $kerFailedToReadImageData
 """
     ]
diff --git a/tests/bugfixes/github/test_issue_1833.py b/tests/bugfixes/github/test_issue_1833.py
index bd5099492b..f55596a659 100644
--- a/tests/bugfixes/github/test_issue_1833.py
+++ b/tests/bugfixes/github/test_issue_1833.py
@@ -12,11 +12,9 @@ class TiffMnEntryDoCountInvalidTiffType(metaclass=CaseMeta):
     url = "https://github.com/Exiv2/exiv2/issues/1833"
 
     filename = path("$data_path/issue_1833_poc.jpg")
-    commands = ["$exiv2 -pS $filename"]
+    commands = [f"$exiv2 -pS {filename}"]
     stderr = [
-        """$exiv2_exception_message """
-        + filename
-        + """:
+        f"""$exiv2_exception_message {filename}:
 $kerFailedToReadImageData
 """
     ]
diff --git a/tests/bugfixes/github/test_issue_1845.py b/tests/bugfixes/github/test_issue_1845.py
index 30d23ef611..84a02b6c11 100644
--- a/tests/bugfixes/github/test_issue_1845.py
+++ b/tests/bugfixes/github/test_issue_1845.py
@@ -15,9 +15,7 @@ class TiffDirectoryWriteDirEntryAssert(metaclass=CaseMeta):
     filename = path("$tmp_path/issue_1845_poc.jp2")
     commands = ["$exiv2 -q -D +1 ad $filename"]
     stderr = [
-        """$exception_in_adjust """
-        + filename
-        + """:
+        f"""$exception_in_adjust {filename}:
 $kerCorruptedMetadata
 """
     ]
diff --git a/tests/bugfixes/github/test_issue_1881.py b/tests/bugfixes/github/test_issue_1881.py
index 748451a1f5..5a0dff2126 100644
--- a/tests/bugfixes/github/test_issue_1881.py
+++ b/tests/bugfixes/github/test_issue_1881.py
@@ -16,9 +16,7 @@ class SonyPreviewImageLargeAllocation(metaclass=CaseMeta):
     filename2 = path("$tmp_path/issue_1881_coverage.jpg")
     commands = ["$exiv2 -q -d I rm $filename1", "$exiv2 -q -d I rm $filename2"]
     stderr = [
-        """$exception_in_erase """
-        + filename1
-        + """:
+        f"""$exception_in_erase {filename1}:
 $kerFailedToReadImageData
 """,
         "",
diff --git a/tests/bugfixes/github/test_issue_20.py b/tests/bugfixes/github/test_issue_20.py
index 6e98b5fdd8..adfd82c0f5 100644
--- a/tests/bugfixes/github/test_issue_20.py
+++ b/tests/bugfixes/github/test_issue_20.py
@@ -13,12 +13,10 @@ class TamronSupport(metaclass=system_tests.CaseMeta):
         "TamronSP90mmF2.8DiVCUSDMacroF004.exv",
         "TamronSP90mmF2.8DiVCUSDMacroF017.exv",
     ]
-    commands = [f"$exiv2 -pa --grep lens/i ../../../test/data/{files[0]}"] + list(
-        map(
-            lambda fname: f"$exiv2 -pa --grep lenstype/i ../../../test/data/{fname}",
-            files[1:],
-        )
-    )
+    commands = [f"$exiv2 -pa --grep lens/i ../../../test/data/{files[0]}"] + [
+        f"$exiv2 -pa --grep lenstype/i ../../../test/data/{fname}"
+        for fname in files[1:]
+    ]
     retval = [0] * len(files)
 
     stdout = [
diff --git a/tests/bugfixes/github/test_issue_227.py b/tests/bugfixes/github/test_issue_227.py
index 2a557c3a76..65e4b6fb93 100644
--- a/tests/bugfixes/github/test_issue_227.py
+++ b/tests/bugfixes/github/test_issue_227.py
@@ -10,9 +10,7 @@ class SigmaLenses(metaclass=system_tests.CaseMeta):
         "Sigma_50mm_F1.4_DG_HSM_A.exv",
     ]
 
-    commands = list(
-        map(lambda fname: f"$exiv2 -pa --grep lens/i $data_path/{fname}", files)
-    )
+    commands = [f"$exiv2 -pa --grep lens/i $data_path/{fname}" for fname in files]
 
     retval = 3 * [0]
     stderr = 3 * [""]
diff --git a/tests/bugfixes/github/test_issue_2270.py b/tests/bugfixes/github/test_issue_2270.py
index cc71aa7bd8..32106a696c 100644
--- a/tests/bugfixes/github/test_issue_2270.py
+++ b/tests/bugfixes/github/test_issue_2270.py
@@ -16,9 +16,7 @@ class WebPImage_inject_VP8X_integer_overflow(metaclass=CaseMeta):
     commands = ["$exiv2 rm $filename"]
     stdout = [""]
     stderr = [
-        """$exception_in_erase """
-        + filename
-        + """:
+        f"""$exception_in_erase {filename}:
 $kerCorruptedMetadata
 """
     ]
diff --git a/tests/bugfixes/github/test_issue_246.py b/tests/bugfixes/github/test_issue_246.py
index 855dcc7f36..50d78fe621 100644
--- a/tests/bugfixes/github/test_issue_246.py
+++ b/tests/bugfixes/github/test_issue_246.py
@@ -12,11 +12,9 @@ class TestFirstPoC(metaclass=system_tests.CaseMeta):
     url = "https://github.com/Exiv2/exiv2/issues/246"
 
     filename = "$data_path/1-string-format.jpg"
-    commands = ["$exiv2 -pS " + filename]
+    commands = [f"$exiv2 -pS {filename}"]
     stdout = [
-        """STRUCTURE OF JPEG FILE: """
-        + filename
-        + """
+        f"""STRUCTURE OF JPEG FILE: {filename}
  address | marker       |  length | data
        0 | 0xffd8 SOI  
        2 | 0xffe1 APP1  |      60 | Exif..II*.....0.i...........0000
@@ -24,9 +22,7 @@ class TestFirstPoC(metaclass=system_tests.CaseMeta):
     ]
 
     stderr = [
-        """$exiv2_exception_message """
-        + filename
-        + """:
+        f"""$exiv2_exception_message {filename}:
 $kerNoImageInInputData
 """
     ]
diff --git a/tests/bugfixes/github/test_issue_253.py b/tests/bugfixes/github/test_issue_253.py
index 04a5c74dae..76bc0b1e79 100644
--- a/tests/bugfixes/github/test_issue_253.py
+++ b/tests/bugfixes/github/test_issue_253.py
@@ -12,12 +12,10 @@ class TestFirstPoC(metaclass=system_tests.CaseMeta):
     url = "https://github.com/Exiv2/exiv2/issues/253"
 
     filename = "$data_path/3-stringformat-outofbound-read"
-    commands = ["$exiv2 " + filename]
+    commands = [f"$exiv2 {filename}"]
     stdout = [""]
     stderr = [
-        """$exiv2_exception_message """
-        + filename
-        + """:
+        f"""$exiv2_exception_message {filename}:
 $kerNotAJpeg
 """
     ]
diff --git a/tests/bugfixes/github/test_issue_400.py b/tests/bugfixes/github/test_issue_400.py
index aa96843adb..61ca7fae0f 100644
--- a/tests/bugfixes/github/test_issue_400.py
+++ b/tests/bugfixes/github/test_issue_400.py
@@ -8,12 +8,10 @@ class parseTXTChunkOutOfBoundsRead(metaclass=system_tests.CaseMeta):
 
     filenames = [system_tests.path("$data_path/issue_400_poc" + str(i)) for i in (1, 2)]
 
-    commands = ["$exiv2 " + fname for fname in filenames]
+    commands = [f"$exiv2 {fname}" for fname in filenames]
     stdout = [""] * 2
     stderr = [
-        """$exiv2_exception_message """
-        + fname
-        + """:
+        f"""$exiv2_exception_message {fname}:
 $kerCorruptedMetadata
 """
         for fname in filenames
diff --git a/tests/bugfixes/github/test_issue_426.py b/tests/bugfixes/github/test_issue_426.py
index 91d97b1655..0de688b909 100644
--- a/tests/bugfixes/github/test_issue_426.py
+++ b/tests/bugfixes/github/test_issue_426.py
@@ -7,12 +7,10 @@ class DetectsWrongLengthOfImageResourceInPSDFile(metaclass=system_tests.CaseMeta
     url = "https://github.com/Exiv2/exiv2/issues/426"
 
     filename = system_tests.path("$data_path/h02.psd")
-    commands = ["$exiv2 " + filename]
+    commands = [f"$exiv2 {filename}"]
     retval = [1]
     stderr = [
-        """$exiv2_exception_message """
-        + filename
-        + """:
+        f"""$exiv2_exception_message {filename}:
 $kerCorruptedMetadata
 """
     ]
diff --git a/tests/bugfixes/github/test_issue_428.py b/tests/bugfixes/github/test_issue_428.py
index 38eebbd305..12d59f8e97 100644
--- a/tests/bugfixes/github/test_issue_428.py
+++ b/tests/bugfixes/github/test_issue_428.py
@@ -4,13 +4,9 @@
 
 
 def stderr_exception(fname):
-    return (
-        """$exiv2_exception_message """
-        + fname
-        + """:
+    return f"""$exiv2_exception_message {fname}:
 $kerFailedToReadImageData
 """
-    )
 
 
 class PngReadRawProfile(metaclass=system_tests.CaseMeta):
@@ -27,14 +23,12 @@ class PngReadRawProfile(metaclass=system_tests.CaseMeta):
         system_tests.path("$data_path/issue_428_poc6.png"),
     ]
 
-    commands = ["$exiv2 " + fname for fname in filenames]
+    commands = [f"$exiv2 {fname}" for fname in filenames]
     stdout = [""] * len(filenames)
     stderr = [stderr_exception(fname) for fname in filenames[0:6]]
 
     stderr.append(
-        """$exiv2_exception_message """
-        + filenames[6]
-        + """:
+        f"""$exiv2_exception_message {filenames[6]}:
 $kerInputDataReadFailed
 """
     )
diff --git a/tests/bugfixes/github/test_issue_460.py b/tests/bugfixes/github/test_issue_460.py
index 69304311a9..dae295c61a 100644
--- a/tests/bugfixes/github/test_issue_460.py
+++ b/tests/bugfixes/github/test_issue_460.py
@@ -7,12 +7,10 @@ class ThrowsWhenCRWImageIsMalformed(metaclass=system_tests.CaseMeta):
     url = "https://github.com/Exiv2/exiv2/issues/460"
 
     filename = system_tests.path("$data_path/issue_460")
-    commands = ["$exiv2 " + filename]
+    commands = [f"$exiv2 {filename}"]
     retval = [1]
     stderr = [
-        """$exiv2_exception_message """
-        + filename
-        + """:
+        f"""$exiv2_exception_message {filename}:
 $kerCorruptedMetadata
 """
     ]
diff --git a/tests/bugfixes/github/test_issue_511.py b/tests/bugfixes/github/test_issue_511.py
index 73665c1f73..daec78b9e6 100644
--- a/tests/bugfixes/github/test_issue_511.py
+++ b/tests/bugfixes/github/test_issue_511.py
@@ -9,18 +9,14 @@ class ThrowsWhenIFDsAreMalformed(metaclass=system_tests.CaseMeta):
     url = "https://github.com/Exiv2/exiv2/issues/511"
 
     filename = system_tests.path("$data_path/pocIssue511")
-    commands = ["$exiv2 -pR " + filename]
+    commands = [f"$exiv2 -pR {filename}"]
     retval = [1]
     stdout = [
-        """STRUCTURE OF TIFF FILE (II): """
-        + filename
-        + """
+        f"""STRUCTURE OF TIFF FILE (II): {filename}
 """
     ]
     stderr = [
-        """$exiv2_exception_message """
-        + filename
-        + """:
+        f"""$exiv2_exception_message {filename}:
 $kerCorruptedMetadata
 """
     ]
diff --git a/tests/bugfixes/github/test_issue_712.py b/tests/bugfixes/github/test_issue_712.py
index 7c02d3f892..5e95334a5b 100644
--- a/tests/bugfixes/github/test_issue_712.py
+++ b/tests/bugfixes/github/test_issue_712.py
@@ -23,9 +23,7 @@ class BigTiffImageRecursionStackExhaustion(metaclass=system_tests.CaseMeta):
     commands = ["$exiv2 -b -u -k pr $filename"]
     stdout = [""]
     stderr = [
-        """$exiv2_exception_message """
-        + filename
-        + """:
+        f"""$exiv2_exception_message {filename}:
 $filename: $kerFileContainsUnknownImageType
 """
     ]
diff --git a/tests/bugfixes/github/test_issue_756.py b/tests/bugfixes/github/test_issue_756.py
index 0094ce21f8..a1ed4f715d 100644
--- a/tests/bugfixes/github/test_issue_756.py
+++ b/tests/bugfixes/github/test_issue_756.py
@@ -7,9 +7,7 @@ class BufferOverReadInNikon1MakerNotePrint0x0088(metaclass=system_tests.CaseMeta
     filename = system_tests.path("$data_path/NikonMakerNotePrint0x088_overread")
     commands = ["$exiv2 -q -pt --grep AFFocusPos $filename"]
     stderr = [
-        """$exiv2_exception_message """
-        + filename
-        + """:
+        f"""$exiv2_exception_message {filename}:
 $kerFailedToReadImageData
 """
     ]
diff --git a/tests/bugfixes/github/test_issue_ghsa_583f_w9pm_99r2.py b/tests/bugfixes/github/test_issue_ghsa_583f_w9pm_99r2.py
index baacf07768..8ee1a2d47e 100644
--- a/tests/bugfixes/github/test_issue_ghsa_583f_w9pm_99r2.py
+++ b/tests/bugfixes/github/test_issue_ghsa_583f_w9pm_99r2.py
@@ -15,9 +15,7 @@ class Jp2ImagePrintStructureICC(metaclass=CaseMeta):
     commands = ["$exiv2 -p C $filename"]
     stdout = [""]
     stderr = [
-        """$exiv2_exception_message """
-        + filename
-        + """:
+        f"""$exiv2_exception_message {filename}:
 $kerCorruptedMetadata
 """
     ]
diff --git a/tests/bugfixes/github/test_issue_ghsa_mxw9_qx4c_6m8v.py b/tests/bugfixes/github/test_issue_ghsa_mxw9_qx4c_6m8v.py
index 69a4cb7bd2..afdf9b05c2 100644
--- a/tests/bugfixes/github/test_issue_ghsa_mxw9_qx4c_6m8v.py
+++ b/tests/bugfixes/github/test_issue_ghsa_mxw9_qx4c_6m8v.py
@@ -16,9 +16,7 @@ class Jp2ImageEncodeJp2HeaderOutOfBoundsRead2(metaclass=CaseMeta):
     commands = ["$exiv2 rm $filename"]
     stdout = [""]
     stderr = [
-        """$exception_in_erase """
-        + filename
-        + """:
+        f"""$exception_in_erase {filename}:
 $kerCorruptedMetadata
 """
     ]
diff --git a/tests/bugfixes/redmine/test_issue_1179.py b/tests/bugfixes/redmine/test_issue_1179.py
index cd83d0f1c9..0fc21646c2 100644
--- a/tests/bugfixes/redmine/test_issue_1179.py
+++ b/tests/bugfixes/redmine/test_issue_1179.py
@@ -19,8 +19,7 @@ class CheckFilmMode(metaclass=system_tests.CaseMeta):
 
     url = "http://dev.exiv2.org/issues/1179"
 
-    commands = list(itertools.chain.from_iterable(
-            make_command(fname) for fname in ORIGINAL_FILES))
+    commands = [cmd for fname in ORIGINAL_FILES for cmd in make_command(fname)]
 
     stdout = [
         """Exif.Fujifilm.Version                        Undefined   4  48 49 51 48
diff --git a/tests/bugfixes/redmine/test_issue_800.py b/tests/bugfixes/redmine/test_issue_800.py
index 0f26197e63..1279427cc4 100644
--- a/tests/bugfixes/redmine/test_issue_800.py
+++ b/tests/bugfixes/redmine/test_issue_800.py
@@ -111,11 +111,7 @@ class MissingPhotoshopIrbTypes(metaclass=system_tests.CaseMeta):
     types = ["8BIM", "AgHg", "DCSR", "PHUT"]
     formats = ["jpg", "psd"]
 
-    commands = list(
-        itertools.chain.from_iterable(
-            make_commands(fname) for fname in FILES
-        )
-    )
+    commands = [cmd for fname in FILES for cmd in make_commands(fname)]
 
     stdout = list(
         itertools.chain.from_iterable(
diff --git a/tests/bugfixes/redmine/test_issue_922.py b/tests/bugfixes/redmine/test_issue_922.py
index af8a292b0a..db0b332ef4 100644
--- a/tests/bugfixes/redmine/test_issue_922.py
+++ b/tests/bugfixes/redmine/test_issue_922.py
@@ -1,6 +1,5 @@
 # -*- coding: utf-8 -*-
 
-import itertools
 import os.path
 
 from system_tests import CaseMeta, path
@@ -31,12 +30,9 @@ class AddMinusPSOption(metaclass=CaseMeta):
     commands = [
         "$exiv2 -pX $bug_jpg_file",
         "$exiv2 -pX $IPTC_file",
-    ] + list(
-        itertools.chain.from_iterable([
-            f"$exiv2 -pX {fname}",
-            f"$exiv2 -pS {fname}"
-        ] for fname in files)
-    )
+    ] + [
+        cmd for fname in files for cmd in [f"$exiv2 -pX {fname}", f"$exiv2 -pS {fname}"]
+    ]
 
     stdout = [
         read_file(
diff --git a/tests/system_tests.py b/tests/system_tests.py
index 925f4a9f5f..08b9f21a6b 100644
--- a/tests/system_tests.py
+++ b/tests/system_tests.py
@@ -846,7 +846,7 @@ def __new__(mcs, clsname, bases, dct):
         # expand all non-private variables by brute force
         # => try all expanding all elements defined in the current class until
         # there is no change in them any more
-        keys = [key for key in list(dct.keys()) if not key.startswith('_')]
+        keys = [key for key in dct if not key.startswith('_')]
         while changed:
             changed = False