Tests: switched to using f-strings.

Previously, it was necessary to support older versions of Python for
compatibility.  F-strings were released in Python 3.6.  Python 3.5 was
marked as unsupported by the end of 2020, so now it's possible to start
using f-strings safely for better readability and performance.

7 files changed, 66 insertions, 70 deletions

diff --git a/test/unit/applications/lang/go.py b/test/unit/applications/lang/go.py
index 14e76362..557753a4 100644
--- a/test/unit/applications/lang/go.py
+++ b/test/unit/applications/lang/go.py
@@ -14,23 +14,21 @@ class TestApplicationGo(TestApplicationProto):
         except subprocess.CalledProcessError:
             return None
 
-        temp_dir = option.temp_dir + '/go/'
+        temp_dir = f'{option.temp_dir}/go/'
 
         if not os.path.exists(temp_dir):
             os.mkdir(temp_dir)
 
-        cache_dir = option.cache_dir + '/go-build'
+        cache_dir = f'{option.cache_dir}/go-build'
 
         if not os.path.exists(cache_dir):
             os.mkdir(cache_dir)
 
         env = os.environ.copy()
-        env['GOPATH'] = option.current_dir + '/build/go'
+        env['GOPATH'] = f'{option.current_dir}/build/go'
         env['GOCACHE'] = cache_dir
 
-        shutil.copy2(
-            option.test_dir + '/go/' + script + '/' + name + '.go', temp_dir
-        )
+        shutil.copy2(f'{option.test_dir}/go/{script}/{name}.go', temp_dir)
 
         if static:
             args = [
@@ -41,21 +39,21 @@ class TestApplicationGo(TestApplicationProto):
                 '-ldflags',
                 '-extldflags "-static"',
                 '-o',
-                temp_dir + name,
-                temp_dir + name + '.go',
+                f'{temp_dir}{name}',
+                f'{temp_dir}{name}.go',
             ]
         else:
             args = [
                 'go',
                 'build',
                 '-o',
-                temp_dir + name,
-                temp_dir + name + '.go',
+                f'{temp_dir}{name}',
+                f'{temp_dir}{name}.go',
             ]
 
-        replace_path = option.current_dir + '/build/go/src/unit.nginx.org/go'
+        replace_path = f'{option.current_dir}/build/go/src/unit.nginx.org/go'
 
-        with open(temp_dir + 'go.mod', 'w') as f:
+        with open(f'{temp_dir}go.mod', 'w') as f:
             f.write(
                 f"""module test/app
 require unit.nginx.org/go v0.0.0
@@ -64,7 +62,7 @@ replace unit.nginx.org/go => {replace_path}
             )
 
         if option.detailed:
-            print("\n$ GOPATH=" + env['GOPATH'] + " " + " ".join(args))
+            print(f'\n$ GOPATH={env["GOPATH"]} {" ".join(args)}')
 
         try:
             output = subprocess.check_output(
@@ -82,18 +80,18 @@ replace unit.nginx.org/go => {replace_path}
     def load(self, script, name='app', **kwargs):
         static_build = False
 
-        wdir = option.test_dir + "/go/" + script
-        executable = option.temp_dir + "/go/" + name
+        wdir = f'{option.test_dir}/go/{script}'
+        executable = f'{option.temp_dir}/go/{name}'
 
         if 'isolation' in kwargs and 'rootfs' in kwargs['isolation']:
             wdir = "/go/"
-            executable = "/go/" + name
+            executable = f"/go/{name}"
             static_build = True
 
         TestApplicationGo.prepare_env(script, name, static=static_build)
 
         conf = {
-            "listeners": {"*:7080": {"pass": "applications/" + script}},
+            "listeners": {"*:7080": {"pass": f"applications/{script}"}},
             "applications": {
                 script: {
                     "type": "external",
diff --git a/test/unit/applications/lang/java.py b/test/unit/applications/lang/java.py
index c8936274..cd955974 100644
--- a/test/unit/applications/lang/java.py
+++ b/test/unit/applications/lang/java.py
@@ -12,10 +12,10 @@ class TestApplicationJava(TestApplicationProto):
     application_type = "java"
 
     def prepare_env(self, script):
-        app_path = option.temp_dir + '/java'
-        web_inf_path = app_path + '/WEB-INF/'
-        classes_path = web_inf_path + 'classes/'
-        script_path = option.test_dir + '/java/' + script + '/'
+        app_path = f'{option.temp_dir}/java'
+        web_inf_path = f'{app_path}/WEB-INF/'
+        classes_path = f'{web_inf_path}classes/'
+        script_path = f'{option.test_dir}/java/{script}/'
 
         if not os.path.isdir(app_path):
             os.makedirs(app_path)
@@ -23,7 +23,7 @@ class TestApplicationJava(TestApplicationProto):
         src = []
 
         for f in os.listdir(script_path):
-            file_path = script_path + f
+            file_path = f'{script_path}{f}'
 
             if f.endswith('.java'):
                 src.append(file_path)
@@ -36,7 +36,7 @@ class TestApplicationJava(TestApplicationProto):
                 if f == 'WEB-INF':
                     continue
 
-                shutil.copytree(file_path, app_path + '/' + f)
+                shutil.copytree(file_path, f'{app_path}/{f}')
                 continue
 
             if f == 'web.xml':
@@ -52,11 +52,11 @@ class TestApplicationJava(TestApplicationProto):
                 os.makedirs(classes_path)
 
             classpath = (
-                option.current_dir + '/build/tomcat-servlet-api-9.0.70.jar'
+                f'{option.current_dir}/build/tomcat-servlet-api-9.0.70.jar'
             )
 
             ws_jars = glob.glob(
-                option.current_dir + '/build/websocket-api-java-*.jar'
+                f'{option.current_dir}/build/websocket-api-java-*.jar'
             )
 
             if not ws_jars:
@@ -74,12 +74,12 @@ class TestApplicationJava(TestApplicationProto):
                 '-d',
                 classes_path,
                 '-classpath',
-                classpath + ':' + ws_jars[0],
+                f'{classpath}:{ws_jars[0]}',
             ]
             javac.extend(src)
 
             if option.detailed:
-                print("\n$ " + " ".join(javac))
+                print(f'\n$ {" ".join(javac)}')
 
             try:
                 subprocess.check_output(javac, stderr=subprocess.STDOUT)
@@ -88,26 +88,24 @@ class TestApplicationJava(TestApplicationProto):
                 raise
 
             except subprocess.CalledProcessError:
-                pytest.fail('Can\'t run javac process.')
+                pytest.fail("Can't run javac process.")
 
     def load(self, script, **kwargs):
         self.prepare_env(script)
 
+        script_path = f'{option.test_dir}/java/{script}/'
         self._load_conf(
             {
-                "listeners": {"*:7080": {"pass": "applications/" + script}},
+                "listeners": {"*:7080": {"pass": f"applications/{script}"}},
                 "applications": {
                     script: {
-                        "unit_jars": option.current_dir + '/build',
+                        "unit_jars": f'{option.current_dir}/build',
                         "type": self.get_application_type(),
                         "processes": {"spare": 0},
-                        "working_directory": option.test_dir
-                        + '/java/'
-                        + script
-                        + '/',
-                        "webapp": option.temp_dir + '/java',
+                        "working_directory": script_path,
+                        "webapp": f'{option.temp_dir}/java',
                     }
                 },
             },
-            **kwargs
+            **kwargs,
         )
diff --git a/test/unit/applications/lang/node.py b/test/unit/applications/lang/node.py
index 5d05c70c..87d5a19c 100644
--- a/test/unit/applications/lang/node.py
+++ b/test/unit/applications/lang/node.py
@@ -13,16 +13,16 @@ class TestApplicationNode(TestApplicationProto):
     def prepare_env(self, script):
         # copy application
         shutil.copytree(
-            option.test_dir + '/node/' + script, option.temp_dir + '/node'
+            f'{option.test_dir}/node/{script}', f'{option.temp_dir}/node'
         )
 
         # copy modules
         shutil.copytree(
-            option.current_dir + '/node/node_modules',
-            option.temp_dir + '/node/node_modules',
+            f'{option.current_dir}/node/node_modules',
+            f'{option.temp_dir}/node/node_modules',
         )
 
-        public_dir(option.temp_dir + '/node')
+        public_dir(f'{option.temp_dir}/node')
 
     def load(self, script, name='app.js', **kwargs):
         self.prepare_env(script)
@@ -43,17 +43,17 @@ class TestApplicationNode(TestApplicationProto):
         self._load_conf(
             {
                 "listeners": {
-                    "*:7080": {"pass": "applications/" + quote(script, '')}
+                    "*:7080": {"pass": f"applications/{quote(script, '')}"}
                 },
                 "applications": {
                     script: {
                         "type": "external",
                         "processes": {"spare": 0},
-                        "working_directory": option.temp_dir + '/node',
+                        "working_directory": f'{option.temp_dir}/node',
                         "executable": '/usr/bin/env',
                         "arguments": arguments,
                     }
                 },
             },
-            **kwargs
+            **kwargs,
         )
diff --git a/test/unit/applications/lang/perl.py b/test/unit/applications/lang/perl.py
index 58b867f0..19852363 100644
--- a/test/unit/applications/lang/perl.py
+++ b/test/unit/applications/lang/perl.py
@@ -6,19 +6,19 @@ class TestApplicationPerl(TestApplicationProto):
     application_type = "perl"
 
     def load(self, script, name='psgi.pl', **kwargs):
-        script_path = option.test_dir + '/perl/' + script
+        script_path = f'{option.test_dir}/perl/{script}'
 
         self._load_conf(
             {
-                "listeners": {"*:7080": {"pass": "applications/" + script}},
+                "listeners": {"*:7080": {"pass": f"applications/{script}"}},
                 "applications": {
                     script: {
                         "type": self.get_application_type(),
                         "processes": {"spare": 0},
                         "working_directory": script_path,
-                        "script": script_path + '/' + name,
+                        "script": f'{script_path}/{name}',
                     }
                 },
             },
-            **kwargs
+            **kwargs,
         )
diff --git a/test/unit/applications/lang/php.py b/test/unit/applications/lang/php.py
index 5319d2ca..1b94c3ae 100644
--- a/test/unit/applications/lang/php.py
+++ b/test/unit/applications/lang/php.py
@@ -9,18 +9,18 @@ class TestApplicationPHP(TestApplicationProto):
     application_type = "php"
 
     def load(self, script, index='index.php', **kwargs):
-        script_path = option.test_dir + '/php/' + script
+        script_path = f'{option.test_dir}/php/{script}'
 
         if kwargs.get('isolation') and kwargs['isolation'].get('rootfs'):
             rootfs = kwargs['isolation']['rootfs']
 
-            if not os.path.exists(rootfs + '/app/php/'):
-                os.makedirs(rootfs + '/app/php/')
+            if not os.path.exists(f'{rootfs}/app/php/'):
+                os.makedirs(f'{rootfs}/app/php/')
 
-            if not os.path.exists(rootfs + '/app/php/' + script):
-                shutil.copytree(script_path, rootfs + '/app/php/' + script)
+            if not os.path.exists(f'{rootfs}/app/php/{script}'):
+                shutil.copytree(script_path, f'{rootfs}/app/php/{script}')
 
-            script_path = '/app/php/' + script
+            script_path = f'/app/php/{script}'
 
         app = {
             "type": self.get_application_type(),
@@ -41,8 +41,8 @@ class TestApplicationPHP(TestApplicationProto):
 
         self._load_conf(
             {
-                "listeners": {"*:7080": {"pass": "applications/" + script}},
+                "listeners": {"*:7080": {"pass": f"applications/{script}"}},
                 "applications": {script: app},
             },
-            **kwargs
+            **kwargs,
         )
diff --git a/test/unit/applications/lang/python.py b/test/unit/applications/lang/python.py
index 3768cf07..0bb69992 100644
--- a/test/unit/applications/lang/python.py
+++ b/test/unit/applications/lang/python.py
@@ -20,18 +20,18 @@ class TestApplicationPython(TestApplicationProto):
         if script[0] == '/':
             script_path = script
         else:
-            script_path = option.test_dir + '/python/' + script
+            script_path = f'{option.test_dir}/python/{script}'
 
         if kwargs.get('isolation') and kwargs['isolation'].get('rootfs'):
             rootfs = kwargs['isolation']['rootfs']
 
-            if not os.path.exists(rootfs + '/app/python/'):
-                os.makedirs(rootfs + '/app/python/')
+            if not os.path.exists(f'{rootfs}/app/python/'):
+                os.makedirs(f'{rootfs}/app/python/')
 
-            if not os.path.exists(rootfs + '/app/python/' + name):
-                shutil.copytree(script_path, rootfs + '/app/python/' + name)
+            if not os.path.exists(f'{rootfs}/app/python/{name}'):
+                shutil.copytree(script_path, f'{rootfs}/app/python/{name}')
 
-            script_path = '/app/python/' + name
+            script_path = f'/app/python/{name}'
 
         app = {
             "type": self.get_application_type(),
@@ -58,9 +58,9 @@ class TestApplicationPython(TestApplicationProto):
         self._load_conf(
             {
                 "listeners": {
-                    "*:7080": {"pass": "applications/" + quote(name, '')}
+                    "*:7080": {"pass": f"applications/{quote(name, '')}"}
                 },
                 "applications": {name: app},
             },
-            **kwargs
+            **kwargs,
         )
diff --git a/test/unit/applications/lang/ruby.py b/test/unit/applications/lang/ruby.py
index 824bfe7f..e0712fc6 100644
--- a/test/unit/applications/lang/ruby.py
+++ b/test/unit/applications/lang/ruby.py
@@ -10,22 +10,22 @@ class TestApplicationRuby(TestApplicationProto):
 
     def prepare_env(self, script):
         shutil.copytree(
-            option.test_dir + '/ruby/' + script,
-            option.temp_dir + '/ruby/' + script,
+            f'{option.test_dir}/ruby/{script}',
+            f'{option.temp_dir}/ruby/{script}',
         )
 
-        public_dir(option.temp_dir + '/ruby/' + script)
+        public_dir(f'{option.temp_dir}/ruby/{script}')
 
     def load(self, script, name='config.ru', **kwargs):
         self.prepare_env(script)
 
-        script_path = option.temp_dir + '/ruby/' + script
+        script_path = f'{option.temp_dir}/ruby/{script}'
 
         app = {
             "type": self.get_application_type(),
             "processes": {"spare": 0},
             "working_directory": script_path,
-            "script": script_path + '/' + name,
+            "script": f'{script_path}/{name}',
         }
 
         for key in [
@@ -36,8 +36,8 @@ class TestApplicationRuby(TestApplicationProto):
 
         self._load_conf(
             {
-                "listeners": {"*:7080": {"pass": "applications/" + script}},
+                "listeners": {"*:7080": {"pass": f"applications/{script}"}},
                 "applications": {script: app},
             },
-            **kwargs
+            **kwargs,
         )