diff --git a/src/common/checksums.cpp b/src/common/checksums.cpp
index f75e84f28..c604842a3 100644
--- a/src/common/checksums.cpp
+++ b/src/common/checksums.cpp
@@ -121,7 +121,7 @@ QByteArray calcAdler32(QIODevice *device)
     QByteArray buf(BUFSIZE, Qt::Uninitialized);
 
     unsigned int adler = adler32(0L, Z_NULL, 0);
-    qint64 size;
+    qint64 size = 0;
     while (!device->atEnd()) {
         size = device->read(buf.data(), BUFSIZE);
         if (size > 0)
@@ -204,9 +204,7 @@ ComputeChecksum::ComputeChecksum(QObject *parent)
 {
 }
 
-ComputeChecksum::~ComputeChecksum()
-{
-}
+ComputeChecksum::~ComputeChecksum() = default;
 
 void ComputeChecksum::setChecksumType(const QByteArray &type)
 {
diff --git a/src/common/filesystembase.cpp b/src/common/filesystembase.cpp
index f41b3a617..6b2271777 100644
--- a/src/common/filesystembase.cpp
+++ b/src/common/filesystembase.cpp
@@ -518,9 +518,9 @@ QString FileSystem::pathtoUNC(const QString &str)
 
     /* replace all occurences of / with the windows native \ */
 
-    for (auto it = longStr.begin(); it != longStr.end(); ++it) {
-        if (*it == QLatin1Char('/')) {
-            *it = QLatin1Char('\\');
+    for (auto &c : longStr) {
+        if (c == QLatin1Char('/')) {
+            c = QLatin1Char('\\');
         }
     }
     return longStr;
diff --git a/src/common/remotepermissions.cpp b/src/common/remotepermissions.cpp
index f714277ed..00827f8f1 100644
--- a/src/common/remotepermissions.cpp
+++ b/src/common/remotepermissions.cpp
@@ -62,7 +62,7 @@ QString RemotePermissions::toString() const
 RemotePermissions RemotePermissions::fromDbValue(const QByteArray &value)
 {
     if (value.isEmpty())
-        return RemotePermissions();
+        return {};
     RemotePermissions perm;
     perm.fromArray(value.constData());
     return perm;
diff --git a/src/common/syncjournaldb.cpp b/src/common/syncjournaldb.cpp
index 79fb9c561..8e2a6d81a 100644
--- a/src/common/syncjournaldb.cpp
+++ b/src/common/syncjournaldb.cpp
@@ -706,7 +706,7 @@ bool SyncJournalDb::updateMetadataTableStructure()
         commitInternal(QStringLiteral("update database structure: add path index"));
     }
 
-    if (1) {
+    if (true) {
         SqlQuery query(_db);
         query.prepare("CREATE INDEX IF NOT EXISTS metadata_parent ON metadata(parent_hash(path));");
         if (!query.exec()) {
diff --git a/src/common/vfs.h b/src/common/vfs.h
index 66fae7e4b..f4ea3d8fa 100644
--- a/src/common/vfs.h
+++ b/src/common/vfs.h
@@ -25,12 +25,12 @@
 #include "syncfilestatus.h"
 #include "pinstate.h"
 
-typedef struct csync_file_stat_s csync_file_stat_t;
+using csync_file_stat_t = struct csync_file_stat_s;
 
 namespace OCC {
 
 class Account;
-typedef QSharedPointer<Account> AccountPtr;
+using AccountPtr = QSharedPointer<Account>;
 class SyncJournalDb;
 class VfsPrivate;
 class SyncFileItem;
@@ -329,7 +329,7 @@ OCSYNC_EXPORT std::unique_ptr<Vfs> createVfsFromPlugin(Vfs::Mode mode);
     namespace { \
     void initPlugin() \
     { \
-        OCC::Vfs::registerPlugin(QStringLiteral(name), []() -> OCC::Vfs * { return new Type; }); \
+        OCC::Vfs::registerPlugin(QStringLiteral(name), []() -> OCC::Vfs * { return new (Type); }); \
     } \
     Q_COREAPP_STARTUP_FUNCTION(initPlugin) \
     }
diff --git a/src/csync/csync_exclude.h b/src/csync/csync_exclude.h
index 7d41a3326..bbb0a2cda 100644
--- a/src/csync/csync_exclude.h
+++ b/src/csync/csync_exclude.h
@@ -66,7 +66,7 @@ class OCSYNC_EXPORT ExcludedFiles : public QObject
 {
     Q_OBJECT
 public:
-    typedef std::tuple<int, int, int> Version;
+    using Version = std::tuple<int, int, int>;
 
     explicit ExcludedFiles(const QString &localPath = QStringLiteral("/"));
     ~ExcludedFiles();
diff --git a/src/csync/std/c_lib.h b/src/csync/std/c_lib.h
index 13b9f1587..84f1004b2 100644
--- a/src/csync/std/c_lib.h
+++ b/src/csync/std/c_lib.h
@@ -18,7 +18,7 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
-#include <stdlib.h> // NOLINT this is sometimes compiled in C mode
-#include <string.h> // NOLINT this is sometimes compiled in C mode
+#include <cstdlib>
+#include <cstring>
 
 #include "c_private.h"
diff --git a/src/csync/std/c_private.h b/src/csync/std/c_private.h
index bfad3b1b9..aaa41417f 100644
--- a/src/csync/std/c_private.h
+++ b/src/csync/std/c_private.h
@@ -39,7 +39,7 @@
 #include <unistd.h>
 #endif
 
-#include <errno.h>  // NOLINT this is sometimes compiled in C mode
+#include <cerrno>
 
 #ifdef __MINGW32__
 #ifndef S_IRGRP
@@ -74,10 +74,10 @@
 
 
 #ifdef _WIN32
-typedef struct stat64 csync_stat_t; // NOLINT this is sometimes compiled in C mode
+using csync_stat_t = struct stat64;
 #define _FILE_OFFSET_BITS 64
 #else
-typedef struct stat csync_stat_t; // NOLINT this is sometimes compiled in C mode
+using csync_stat_t = struct stat;
 #endif
 
 #ifndef O_NOATIME
@@ -94,7 +94,7 @@ typedef struct stat csync_stat_t; // NOLINT this is sometimes compiled in C mode
 #endif
 
 #if defined _WIN32 && defined _UNICODE
-typedef  wchar_t         mbchar_t; // NOLINT this is sometimes compiled in C mode
+using mbchar_t = wchar_t;
 #define _topen           _wopen
 #define _tdirent         _wdirent
 #define _topendir        _wopendir
@@ -115,7 +115,7 @@ typedef  wchar_t         mbchar_t; // NOLINT this is sometimes compiled in C mod
 #define _tchdir          _wchdir
 #define _tgetcwd         _wgetcwd
 #else
-typedef char           mbchar_t; // NOLINT this is sometimes compiled in C mode
+using mbchar_t = char;
 #define _tdirent       dirent
 #define _topen         open
 #define _topendir      opendir
diff --git a/src/csync/vio/csync_vio_local_unix.cpp b/src/csync/vio/csync_vio_local_unix.cpp
index 5ebec53a8..1f41f42f1 100644
--- a/src/csync/vio/csync_vio_local_unix.cpp
+++ b/src/csync/vio/csync_vio_local_unix.cpp
@@ -74,7 +74,7 @@ int csync_vio_local_closedir(csync_vio_handle_t *dhandle) {
 
 std::unique_ptr<csync_file_stat_t> csync_vio_local_readdir(csync_vio_handle_t *handle, OCC::Vfs *vfs) {
 
-  struct _tdirent *dirent = NULL;
+  struct _tdirent *dirent = nullptr;
   std::unique_ptr<csync_file_stat_t> file_stat;
 
   do {
diff --git a/src/gui/creds/httpcredentialsgui.cpp b/src/gui/creds/httpcredentialsgui.cpp
index bb588fe0b..f8e3e5f9b 100644
--- a/src/gui/creds/httpcredentialsgui.cpp
+++ b/src/gui/creds/httpcredentialsgui.cpp
@@ -113,7 +113,7 @@ void HttpCredentialsGui::showDialog()
             + QLatin1String("<br>");
     }
 
-    QInputDialog *dialog = new QInputDialog();
+    auto *dialog = new QInputDialog();
     dialog->setAttribute(Qt::WA_DeleteOnClose, true);
     dialog->setWindowTitle(tr("Enter Password"));
     dialog->setLabelText(msg);
diff --git a/src/gui/folder.cpp b/src/gui/folder.cpp
index 7aef17696..742981195 100644
--- a/src/gui/folder.cpp
+++ b/src/gui/folder.cpp
@@ -648,8 +648,8 @@ void Folder::setVirtualFilesEnabled(bool enabled)
         _vfs->stop();
         _vfs->unregisterFolder();
 
-        disconnect(_vfs.data(), 0, this, 0);
-        disconnect(&_engine->syncFileStatusTracker(), 0, _vfs.data(), 0);
+        disconnect(_vfs.data(), nullptr, this, nullptr);
+        disconnect(&_engine->syncFileStatusTracker(), nullptr, _vfs.data(), nullptr);
 
         _vfs.reset(createVfsFromPlugin(newMode).release());
 
diff --git a/src/gui/folderman.cpp b/src/gui/folderman.cpp
index 87ecc4fb9..1e48367a1 100644
--- a/src/gui/folderman.cpp
+++ b/src/gui/folderman.cpp
@@ -1007,7 +1007,7 @@ Folder *FolderMan::addFolder(AccountState *accountState, const FolderDefinition
     auto vfs = createVfsFromPlugin(folderDefinition.virtualFilesMode);
     if (!vfs) {
         qCWarning(lcFolderMan) << "Could not load plugin for mode" << folderDefinition.virtualFilesMode;
-        return 0;
+        return nullptr;
     }
 
     auto folder = addFolderInternal(definition, accountState, std::move(vfs));
diff --git a/src/gui/guiutility.cpp b/src/gui/guiutility.cpp
index 596f5a891..427ebb4b2 100644
--- a/src/gui/guiutility.cpp
+++ b/src/gui/guiutility.cpp
@@ -79,7 +79,6 @@ QString Utility::vfsCurrentAvailabilityText(VfsItemAvailability availability)
     case VfsItemAvailability::Mixed:
         return QCoreApplication::translate("utility", "Some available online only");
     case VfsItemAvailability::AllDehydrated:
-        return QCoreApplication::translate("utility", "Available online only");
     case VfsItemAvailability::OnlineOnly:
         return QCoreApplication::translate("utility", "Available online only");
     }
diff --git a/src/gui/settingsdialog.cpp b/src/gui/settingsdialog.cpp
index 511d19b8b..1a06a5ec1 100644
--- a/src/gui/settingsdialog.cpp
+++ b/src/gui/settingsdialog.cpp
@@ -246,7 +246,7 @@ void SettingsDialog::accountAdded(AccountState *s)
 
     if (!brandingSingleAccount) {
         accountAction->setToolTip(s->account()->displayName());
-        accountAction->setIconText(shortDisplayNameForSettings(s->account().data(), height * buttonSizeRatio));
+        accountAction->setIconText(shortDisplayNameForSettings(s->account().data(), static_cast<int>(height * buttonSizeRatio)));
     }
 
     _toolBar->insertAction(_toolBar->actions().at(0), accountAction);
@@ -295,7 +295,7 @@ void SettingsDialog::slotAccountDisplayNameChanged()
             QString displayName = account->displayName();
             action->setText(displayName);
             auto height = _toolBar->sizeHint().height();
-            action->setIconText(shortDisplayNameForSettings(account, height * buttonSizeRatio));
+            action->setIconText(shortDisplayNameForSettings(account, static_cast<int>(height * buttonSizeRatio)));
         }
     }
 }
diff --git a/src/libsync/creds/httpcredentials.cpp b/src/libsync/creds/httpcredentials.cpp
index 21bb5559c..aa608759e 100644
--- a/src/libsync/creds/httpcredentials.cpp
+++ b/src/libsync/creds/httpcredentials.cpp
@@ -201,7 +201,7 @@ void HttpCredentials::fetchFromKeychainHelper()
     if (!_clientCertBundle.isEmpty()) {
         // New case (>=2.6): We have a bundle in the settings and read the password from
         // the keychain
-        ReadPasswordJob *job = new ReadPasswordJob(Theme::instance()->appName());
+        auto job = new ReadPasswordJob(Theme::instance()->appName());
         addSettingsToJob(_account, job);
         job->setInsecureFallback(false);
         job->setKey(keychainKey(_account->url().toString(), _user + clientCertPasswordC, _account->id()));
@@ -263,7 +263,7 @@ void HttpCredentials::slotReadClientCertPasswordJobDone(QKeychain::Job *job)
     if (keychainUnavailableRetryLater(job))
         return;
 
-    ReadPasswordJob *readJob = static_cast<ReadPasswordJob *>(job);
+    auto readJob = static_cast<ReadPasswordJob *>(job);
     if (readJob->error() == NoError) {
         _clientCertPassword = readJob->binaryData();
     } else {
diff --git a/src/libsync/creds/tokencredentials.cpp b/src/libsync/creds/tokencredentials.cpp
index 2e443065e..85b5032ce 100644
--- a/src/libsync/creds/tokencredentials.cpp
+++ b/src/libsync/creds/tokencredentials.cpp
@@ -41,7 +41,7 @@ class TokenCredentialsAccessManager : public AccessManager
 {
 public:
     friend class TokenCredentials;
-    TokenCredentialsAccessManager(const TokenCredentials *cred, QObject *parent = 0)
+    TokenCredentialsAccessManager(const TokenCredentials *cred, QObject *parent = nullptr)
         : AccessManager(parent)
         , _cred(cred)
     {
diff --git a/src/libsync/discovery.cpp b/src/libsync/discovery.cpp
index 3a1c311c1..120dc197a 100644
--- a/src/libsync/discovery.cpp
+++ b/src/libsync/discovery.cpp
@@ -1296,9 +1296,8 @@ auto ProcessDirectoryJob::checkMovePermissions(RemotePermissions srcPerm, const
     bool destinationOK = true;
     bool destinationNewOK = true;
     if (destPerms.isNull()) {
-    } else if (isDirectory && !destPerms.hasPermission(RemotePermissions::CanAddSubDirectories)) {
-        destinationNewOK = false;
-    } else if (!isDirectory && !destPerms.hasPermission(RemotePermissions::CanAddFile)) {
+    } else if ((isDirectory && !destPerms.hasPermission(RemotePermissions::CanAddSubDirectories)) ||
+              (!isDirectory && !destPerms.hasPermission(RemotePermissions::CanAddFile))) {
         destinationNewOK = false;
     }
     if (!isRename && !destinationNewOK) {
diff --git a/src/libsync/discoveryphase.h b/src/libsync/discoveryphase.h
index 20aab7311..7e31389c2 100644
--- a/src/libsync/discoveryphase.h
+++ b/src/libsync/discoveryphase.h
@@ -89,7 +89,7 @@ class DiscoverySingleLocalDirectoryJob : public QObject, public QRunnable
 {
     Q_OBJECT
 public:
-    explicit DiscoverySingleLocalDirectoryJob(const AccountPtr &account, const QString &localPath, OCC::Vfs *vfs, QObject *parent = 0);
+    explicit DiscoverySingleLocalDirectoryJob(const AccountPtr &account, const QString &localPath, OCC::Vfs *vfs, QObject *parent = nullptr);
 
     void run() Q_DECL_OVERRIDE;
 signals:
diff --git a/src/libsync/localdiscoverytracker.cpp b/src/libsync/localdiscoverytracker.cpp
index e7b42308b..2e8bc6716 100644
--- a/src/libsync/localdiscoverytracker.cpp
+++ b/src/libsync/localdiscoverytracker.cpp
@@ -22,9 +22,7 @@ using namespace OCC;
 
 Q_LOGGING_CATEGORY(lcLocalDiscoveryTracker, "sync.localdiscoverytracker", QtInfoMsg)
 
-LocalDiscoveryTracker::LocalDiscoveryTracker()
-{
-}
+LocalDiscoveryTracker::LocalDiscoveryTracker() = default;
 
 void LocalDiscoveryTracker::addTouchedPath(const QString &relativePath)
 {
diff --git a/src/libsync/localdiscoverytracker.h b/src/libsync/localdiscoverytracker.h
index 1893e9402..b813ea97e 100644
--- a/src/libsync/localdiscoverytracker.h
+++ b/src/libsync/localdiscoverytracker.h
@@ -24,7 +24,7 @@
 namespace OCC {
 
 class SyncFileItem;
-typedef QSharedPointer<SyncFileItem> SyncFileItemPtr;
+using SyncFileItemPtr = QSharedPointer<SyncFileItem>;
 
 /**
  * @brief Tracks files that must be rediscovered locally
diff --git a/src/libsync/propagatedownload.cpp b/src/libsync/propagatedownload.cpp
index 52df7bd60..161b191df 100644
--- a/src/libsync/propagatedownload.cpp
+++ b/src/libsync/propagatedownload.cpp
@@ -205,7 +205,7 @@ void GETFileJob::slotMetaDataChanged()
         return;
     }
 
-    bool ok;
+    bool ok = false;
     _contentLength = reply()->header(QNetworkRequest::ContentLengthHeader).toLongLong(&ok);
     if (ok && _expectedContentLength != -1 && _contentLength != _expectedContentLength) {
         qCWarning(lcGetJob) << "We received a different content length than expected!"
diff --git a/src/libsync/propagateupload.cpp b/src/libsync/propagateupload.cpp
index d2182df81..0cbb73ec6 100644
--- a/src/libsync/propagateupload.cpp
+++ b/src/libsync/propagateupload.cpp
@@ -441,12 +441,7 @@ UploadDevice::UploadDevice(const QString &fileName, qint64 start, qint64 size, B
     : _file(fileName)
     , _start(start)
     , _size(size)
-    , _read(0)
     , _bandwidthManager(bwm)
-    , _bandwidthQuota(0)
-    , _readWithProgress(0)
-    , _bandwidthLimited(false)
-    , _choked(false)
 {
     _bandwidthManager->registerUploadDevice(this);
 }
diff --git a/src/libsync/propagateupload.h b/src/libsync/propagateupload.h
index f9e239abd..d04f10172 100644
--- a/src/libsync/propagateupload.h
+++ b/src/libsync/propagateupload.h
@@ -73,10 +73,10 @@ private:
 
     // Bandwidth manager related
     QPointer<BandwidthManager> _bandwidthManager;
-    qint64 _bandwidthQuota;
-    qint64 _readWithProgress;
-    bool _bandwidthLimited; // if _bandwidthQuota will be used
-    bool _choked; // if upload is paused (readData() will return 0)
+    qint64 _bandwidthQuota = 0;
+    qint64 _readWithProgress = 0;
+    bool _bandwidthLimited = false; // if _bandwidthQuota will be used
+    bool _choked = false; // if upload is paused (readData() will return 0)
     friend class BandwidthManager;
 public slots:
     void slotJobUploadProgress(qint64 sent, qint64 t);
diff --git a/src/libsync/syncengine.cpp b/src/libsync/syncengine.cpp
index 834bfe74d..9c2dd8edc 100644
--- a/src/libsync/syncengine.cpp
+++ b/src/libsync/syncengine.cpp
@@ -563,7 +563,7 @@ void SyncEngine::startSync()
         // files with names that contain these.
         // It's important to respect the capability also for older servers -- the
         // version check doesn't make sense for custom servers.
-        invalidFilenamePattern = "[\\\\:?*\"<>|]";
+        invalidFilenamePattern = R"([\\:?*"<>|])";
     }
     if (!invalidFilenamePattern.isEmpty())
         _discoveryPhase->_invalidFilenameRx = QRegExp(invalidFilenamePattern);
@@ -589,12 +589,10 @@ void SyncEngine::startSync()
 void SyncEngine::slotFolderDiscovered(bool local, const QString &folder)
 {
     // Don't wanna overload the UI
-    if (!_lastUpdateProgressCallbackCall.isValid()) {
-        _lastUpdateProgressCallbackCall.start(); // first call
-    } else if (_lastUpdateProgressCallbackCall.elapsed() < 200) {
-        return;
+    if (!_lastUpdateProgressCallbackCall.isValid() || _lastUpdateProgressCallbackCall.elapsed() >= 200) {
+        _lastUpdateProgressCallbackCall.start(); // first call or enough elapsed time
     } else {
-        _lastUpdateProgressCallbackCall.start();
+        return;
     }
 
     if (local) {
@@ -1014,7 +1012,7 @@ void SyncEngine::abort()
     } else if (_discoveryPhase) {
         // Delete the discovery and all child jobs after ensuring
         // it can't finish and start the propagator
-        disconnect(_discoveryPhase.data(), 0, this, 0);
+        disconnect(_discoveryPhase.data(), nullptr, this, nullptr);
         _discoveryPhase.take()->deleteLater();
 
         syncError(tr("Aborted"));
diff --git a/src/libsync/vfs/suffix/vfs_suffix.cpp b/src/libsync/vfs/suffix/vfs_suffix.cpp
index 357d5c88e..40a7519a7 100644
--- a/src/libsync/vfs/suffix/vfs_suffix.cpp
+++ b/src/libsync/vfs/suffix/vfs_suffix.cpp
@@ -27,9 +27,7 @@ VfsSuffix::VfsSuffix(QObject *parent)
 {
 }
 
-VfsSuffix::~VfsSuffix()
-{
-}
+VfsSuffix::~VfsSuffix() = default;
 
 Vfs::Mode VfsSuffix::mode() const
 {
diff --git a/test/csync/vio_tests/check_vio_ext.cpp b/test/csync/vio_tests/check_vio_ext.cpp
index 209798988..193a9be47 100644
--- a/test/csync/vio_tests/check_vio_ext.cpp
+++ b/test/csync/vio_tests/check_vio_ext.cpp
@@ -61,7 +61,7 @@ static int wipe_testdir()
 }
 
 static int setup_testenv(void **state) {
-    int rc;
+    int rc = 0;
 
     rc = wipe_testdir();
     assert_int_equal(rc, 0);
@@ -80,7 +80,7 @@ static int setup_testenv(void **state) {
     assert_int_equal(rc, 0);
 
     /* --- initialize csync */
-    statevar *mystate = new statevar;
+    auto mystate = new statevar;
     *state = mystate;
     return 0;
 }
@@ -91,7 +91,7 @@ static void output( const char *text )
 }
 
 static int teardown(void **state) {
-    int rc;
+    int rc = -1;
 
     output("================== Tearing down!\n");
 
@@ -110,7 +110,7 @@ static int teardown(void **state) {
  */
 static void create_dirs( const char *path )
 {
-  int rc;
+  int rc = -1;
   auto _mypath = QStringLiteral("%1/%2").arg(CSYNC_TEST_DIR, QString::fromUtf8(path)).toUtf8();
   char *mypath = _mypath.data();
 
@@ -149,13 +149,13 @@ static void create_dirs( const char *path )
  */
 static void traverse_dir(void **state, const QString &dir, int *cnt)
 {
-    csync_vio_handle_t *dh;
+    csync_vio_handle_t *dh = nullptr;
     std::unique_ptr<csync_file_stat_t> dirent;
-    statevar *sv = (statevar*) *state;
+    auto sv = (statevar*) *state;
     QByteArray subdir;
     QByteArray subdir_out;
-    int rc;
-    int is_dir;
+    int rc = -1;
+    int is_dir = 0;
 
     dh = csync_vio_local_opendir(dir);
     assert_non_null(dh);
@@ -208,7 +208,7 @@ static void create_file( const char *path, const char *name, const char *content
 
 static void check_readdir_shorttree(void **state)
 {
-    statevar *sv = (statevar*) *state;
+    auto sv = (statevar*) *state;
 
     const char *t1 = "alibaba/und/die/vierzig/räuber/";
     create_dirs( t1 );
@@ -230,7 +230,7 @@ static void check_readdir_shorttree(void **state)
 
 static void check_readdir_with_content(void **state)
 {
-    statevar *sv = (statevar*) *state;
+    auto sv = (statevar*) *state;
     int files_cnt = 0;
 
     const char *t1 = "warum/nur/40/Räuber/";
@@ -257,7 +257,7 @@ static void check_readdir_with_content(void **state)
 
 static void check_readdir_longtree(void **state)
 {
-    statevar *sv = (statevar*) *state;
+    auto sv = (statevar*) *state;
 
     /* Strange things here: Compilers only support strings with length of 4k max.
      * The expected result string is longer, so it needs to be split up in r1, r2 and r3
@@ -327,7 +327,7 @@ static void check_readdir_longtree(void **state)
 // https://github.com/owncloud/client/issues/3128 https://github.com/owncloud/client/issues/2777
 static void check_readdir_bigunicode(void **state)
 {
-    statevar *sv = (statevar*) *state;
+    auto sv = (statevar*) *state;
 //    1: ? ASCII: 239 - EF
 //    2: ? ASCII: 187 - BB
 //    3: ? ASCII: 191 - BF
@@ -362,5 +362,5 @@ int torture_run_tests(void)
         cmocka_unit_test_setup_teardown(check_readdir_bigunicode, setup_testenv, teardown),
     };
 
-    return cmocka_run_group_tests(tests, NULL, NULL);
+    return cmocka_run_group_tests(tests, nullptr, nullptr);
 }
diff --git a/test/mockserver/httpserver.h b/test/mockserver/httpserver.h
index b408e4233..91bd5899e 100644
--- a/test/mockserver/httpserver.h
+++ b/test/mockserver/httpserver.h
@@ -18,7 +18,7 @@ class HttpServer : public QTcpServer
  {
      Q_OBJECT
  public:
-    HttpServer(qint16 port, QObject* parent = 0);
+    HttpServer(qint16 port, QObject* parent = nullptr);
     void incomingConnection(int socket);
 
  private slots:
diff --git a/test/syncenginetestutils.cpp b/test/syncenginetestutils.cpp
index 640cadf8d..aba75d6c4 100644
--- a/test/syncenginetestutils.cpp
+++ b/test/syncenginetestutils.cpp
@@ -8,6 +8,10 @@
 #include "syncenginetestutils.h"
 
 
+#include <memory>
+
+
+
 PathComponents::PathComponents(const char *path)
     : PathComponents { QString::fromUtf8(path) }
 {
@@ -374,7 +378,7 @@ FileInfo *FakePutReply::perform(FileInfo &remoteRootFileInfo, const QNetworkRequ
         fileInfo = remoteRootFileInfo.create(fileName, putPayload.size(), putPayload.at(0));
     }
     fileInfo->lastModified = OCC::Utility::qDateTimeFromTime_t(request.rawHeader("X-OC-Mtime").toLongLong());
-    remoteRootFileInfo.find(fileName, /*invalidate_etags=*/true);
+    remoteRootFileInfo.find(fileName, /*invalidateEtags=*/true);
     return fileInfo;
 }
 
@@ -612,7 +616,7 @@ FileInfo *FakeChunkMoveReply::perform(FileInfo &uploadsFileInfo, FileInfo &remot
     QString source = getFilePathFromUrl(request.url());
     Q_ASSERT(!source.isEmpty());
     Q_ASSERT(source.endsWith(QLatin1String("/.file")));
-    source = source.left(source.length() - qstrlen("/.file"));
+    source = source.left(source.length() - static_cast<int>(qstrlen("/.file")));
 
     auto sourceFolder = uploadsFileInfo.find(source);
     Q_ASSERT(sourceFolder);
@@ -657,7 +661,7 @@ FileInfo *FakeChunkMoveReply::perform(FileInfo &uploadsFileInfo, FileInfo &remot
         fileInfo = remoteRootFileInfo.create(fileName, size, payload);
     }
     fileInfo->lastModified = OCC::Utility::qDateTimeFromTime_t(request.rawHeader("X-OC-Mtime").toLongLong());
-    remoteRootFileInfo.find(fileName, /*invalidate_etags=*/true);
+    remoteRootFileInfo.find(fileName, /*invalidateEtags=*/true);
 
     return fileInfo;
 }
@@ -800,7 +804,7 @@ QNetworkReply *FakeQNAM::createRequest(QNetworkAccessManager::Operation op, cons
     FileInfo &info = isUpload ? _uploadFileInfo : _remoteRootFileInfo;
 
     auto verb = request.attribute(QNetworkRequest::CustomVerbAttribute);
-    FakeReply *reply;
+    FakeReply *reply = nullptr;
     if (verb == QLatin1String("PROPFIND"))
         // Ignore outgoingData always returning somethign good enough, works for now.
         reply = new FakePropfindReply { info, op, request, this };
@@ -841,8 +845,8 @@ FakeFolder::FakeFolder(const FileInfo &fileTemplate)
     _account->setDavDisplayName(QStringLiteral("fakename"));
     _account->setServerVersion(QStringLiteral("10.0.0"));
 
-    _journalDb.reset(new OCC::SyncJournalDb(localPath() + QStringLiteral(".sync_test.db")));
-    _syncEngine.reset(new OCC::SyncEngine(_account, localPath(), QString(), _journalDb.get()));
+    _journalDb = std::make_unique<OCC::SyncJournalDb>(localPath() + QStringLiteral(".sync_test.db"));
+    _syncEngine = std::make_unique<OCC::SyncEngine>(_account, localPath(), QString(), _journalDb.get());
     // Ignore temporary files from the download. (This is in the default exclude list, but we don't load it)
     _syncEngine->excludedFiles().addManualExclude(QStringLiteral("]*.~*"));
 
@@ -1026,5 +1030,4 @@ FakeReply::FakeReply(QObject *parent)
 }
 
 FakeReply::~FakeReply()
-{
-}
+= default;
diff --git a/test/testasyncop.cpp b/test/testasyncop.cpp
index 29cfa1457..22b5c57f9 100644
--- a/test/testasyncop.cpp
+++ b/test/testasyncop.cpp
@@ -113,7 +113,7 @@ private slots:
         auto successCallback = [](TestCase *tc, const QNetworkRequest &request) {
             tc->pollRequest = [](TestCase *, const QNetworkRequest &) -> QNetworkReply * { std::abort(); }; // shall no longer be called
             FileInfo *info = tc->perform();
-            QByteArray body = "{ \"status\":\"finished\", \"ETag\":\"\\\"" + info->etag + "\\\"\", \"fileId\":\"" + info->fileId + "\"}\n";
+            QByteArray body = R"({ "status":"finished", "ETag":"\")" + info->etag + R"(\"", "fileId":")" + info->fileId + "\"}\n";
             return new FakePayloadReply(QNetworkAccessManager::GetOperation, request, body, nullptr);
         };
         // Callback that never finishes
@@ -139,7 +139,7 @@ private slots:
         };
 
         // Create a testcase by creating a file of a given size locally and assigning it a callback
-        auto insertFile = [&](const QString &file, int size, TestCase::PollRequest_t cb) {
+        auto insertFile = [&](const QString &file, qint64 size, TestCase::PollRequest_t cb) {
             fakeFolder.localModifier().insert(file, size);
             testCases[file] = { std::move(cb) };
         };
diff --git a/test/testdownload.cpp b/test/testdownload.cpp
index ec451e07b..80d85e4bd 100644
--- a/test/testdownload.cpp
+++ b/test/testdownload.cpp
@@ -26,7 +26,7 @@ public:
     {
         if (aborted)
             return 0;
-        return std::min(size, fakeSize) + QIODevice::bytesAvailable();
+        return std::min(size, fakeSize) + QIODevice::bytesAvailable(); // NOLINT: This is intended to simulare the brokeness
     }
 
     qint64 readData(char *data, qint64 maxlen) override
diff --git a/test/testexcludedfiles.cpp b/test/testexcludedfiles.cpp
index f00683e88..c91b918fc 100644
--- a/test/testexcludedfiles.cpp
+++ b/test/testexcludedfiles.cpp
@@ -666,7 +666,7 @@ private slots:
     {
         extern void csync_exclude_expand_escapes(QByteArray &input);
 
-        QByteArray line = "keep \\' \\\" \\? \\\\ \\a \\b \\f \\n \\r \\t \\v \\z \\#";
+        QByteArray line = R"(keep \' \" \? \\ \a \b \f \n \r \t \v \z \#)";
         csync_exclude_expand_escapes(line);
         QVERIFY(0 == strcmp(line.constData(), "keep ' \" ? \\\\ \a \b \f \n \r \t \v \\z #"));
 
diff --git a/test/testoauth.cpp b/test/testoauth.cpp
index 506156a76..a366407db 100644
--- a/test/testoauth.cpp
+++ b/test/testoauth.cpp
@@ -310,14 +310,14 @@ private slots:
                 if (redirectsDone == 0) {
                     std::unique_ptr<QBuffer> payload(new QBuffer());
                     payload->setData("");
-                    SlowFakePostReply *reply = new SlowFakePostReply(op, request, std::move(payload), this);
+                    auto *reply = new SlowFakePostReply(op, request, std::move(payload), this);
                     reply->redirectToPolicy = true;
                     redirectsDone++;
                     return reply;
                 } else if  (redirectsDone == 1) {
                     std::unique_ptr<QBuffer> payload(new QBuffer());
                     payload->setData("");
-                    SlowFakePostReply *reply = new SlowFakePostReply(op, request, std::move(payload), this);
+                    auto *reply = new SlowFakePostReply(op, request, std::move(payload), this);
                     reply->redirectToToken = true;
                     redirectsDone++;
                     return reply;