diff --git a/.gitignore b/.gitignore
index 6771257681ccf703707aa8a3e22c7de7f92e776a..7febe331aa95369855ec5f58592c7dbb6cca9987 100644
--- a/.gitignore
+++ b/.gitignore
@@ -11,4 +11,8 @@
 # Cache
 .cache
 # Egg
-analysis.egg-info
\ No newline at end of file
+analysis.egg-info
+# coverage.py report
+*.coverage
+*.xml
+*.gitignore
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
new file mode 100644
index 0000000000000000000000000000000000000000..19161ab959d7b2f5c94da788007cb424717c2c8f
--- /dev/null
+++ b/.gitlab-ci.yml
@@ -0,0 +1,113 @@
+
+stages:
+  - test
+  - deploy
+
+test27:
+#  image: continuumio/anaconda
+  image: continuumio/miniconda:latest
+  stage: test
+  script:
+    - echo "========== Setting up environment =========="
+    - apt install -y python-dev > tmp.txt && echo 'apt deps installed'
+    - conda config --set always_yes yes --set changeps1 no
+    - conda info -a
+    - conda config --add channels https://conda.anaconda.org/NLeSC  # ROOT channel
+    - conda create -n test27 python=2.7 root=6 root-numpy libgcc gcc make cmake > tmp.txt && echo 'env created'
+    - source activate test27 > tmp.txt && echo 'activated'
+
+#   HACK, psutil fails to build currently
+    - echo "========== HACK install psutil (fails to build) =========="
+    - conda install psutil > tmp.txt && echo 'psutil installed'
+
+#   HACK, subprocess32 fails to build currently
+    - echo "========== HACK install subprocess32 (fails to build) =========="
+    - conda install subprocess32 > tmp.txt && echo 'subprocess32 installed'
+
+    - echo "========== Install analysis =========="
+    - pip install -e .
+
+    - bash ci/test_runner.sh
+
+    - bash ci/static_checker.sh
+
+    - bash ci/testbuild_docs.sh
+
+    - echo "========== All tests finished =========="
+
+test36:
+  image: continuumio/miniconda3:latest
+  stage: test
+  script:
+    - echo "========== Setting up environment =========="
+    - apt install -y python3-dev  > tmp.txt && echo 'apt deps installed'
+    - conda config --set always_yes yes --set changeps1 no
+    - conda info -a
+    - conda config --add channels https://conda.anaconda.org/NLeSC  # ROOT channel
+    - conda create -n test36 python=3.6 root=6 root-numpy libgcc gcc make cmake > tmp.txt && echo 'env created'
+    - source activate test36 > tmp.txt && echo 'activated'
+
+#   HACK, psutil fails to build currently
+    - echo "========== HACK install psutil (fails to build) =========="
+    - conda install psutil > tmp.txt && echo 'psutil installed'
+
+    - echo "========== Install analysis =========="
+    - pip install -e .
+
+    - bash ci/test_runner.sh
+
+    - bash ci/static_checker.sh
+
+    - bash ci/testbuild_docs.sh
+
+
+    - echo "========== All tests finished =========="
+
+
+test36_data_fail:
+  image: continuumio/miniconda3:latest
+  stage: test
+  allow_failure: true
+  script:
+    - echo "========== Setting up environment =========="
+    - apt install -y python3-dev  > tmp.txt && echo 'apt deps installed'
+    - conda config --set always_yes yes --set changeps1 no
+    - conda info -a
+    - conda config --add channels https://conda.anaconda.org/NLeSC  # ROOT channel
+    - conda create -n test36 python=3.6 root=6 root-numpy libgcc gcc make cmake > tmp.txt && echo 'env created'
+    - source activate test36 > tmp.txt && echo 'activated'
+
+#   HACK, psutil fails to build currently
+    - echo "========== HACK install psutil (fails to build) =========="
+    - conda install psutil > tmp.txt && echo 'psutil installed'
+
+    - echo "========== Install analysis =========="
+    - pip install -e .
+
+#   install test utilities
+    - echo "========== Install test utilities =========="
+    - conda install pytest coverage > tmp.txt && echo 'test utils installed'
+
+#    run tests
+    - echo "========== Running tests with coverage =========="
+    - pytest tests/test_data.py  # fails for some unknown reason
+
+
+build_apidoc:
+  image: continuumio/miniconda3:latest
+  stage: deploy
+  only:
+    - master
+  script:
+    - echo "========== Building docs =========="
+    - echo "NotImplementedNotImplementedNotImplementedNotImplemented"
+    - echo "========== Finished building and deploying docs =========="
+
+# Job: run PyLint
+
+#run_pylint:
+#  image: continuumio/miniconda3:latest
+#  type: test
+#  script:
+#    - conda install -y pylint
+#    - pylint analysis/*/*.py || echo "========= Pylint run with errorcode > 0 ========"
diff --git a/analysis/data/hdf.py b/analysis/data/hdf.py
index e0621b29027e8a86a1eae68fd27fdf36175dc3d9..5b34dca126b61d799679eba5f3552233d6f91e52 100644
--- a/analysis/data/hdf.py
+++ b/analysis/data/hdf.py
@@ -37,7 +37,14 @@ def modify_hdf(file_name, compress=True):
         `pandas.HDFStore`: Store to modify.
 
     """
-    mode = 'a' if os.path.exists(file_name) else 'w'
+    mode = 'w'
+    if os.path.exists(file_name):
+        with pd.HDFStore(file_name, mode='a', format='table') as test_len_file:
+            if len(test_len_file) > 0:
+                mode = 'a'
+            else:
+                logger.info("File %s exists but seems empty -> not construct with pytables?"
+                            "Overwritting existing file!", file_name)
     with pd.HDFStore(file_name, mode=mode, format='table') as data_file:
         yield data_file
     logger.debug('Compressing...')
diff --git a/ci/pylintrc b/ci/pylintrc
new file mode 100644
index 0000000000000000000000000000000000000000..42851e38e4e582311183ea08e9bf9ba1a9d503ce
--- /dev/null
+++ b/ci/pylintrc
@@ -0,0 +1,425 @@
+[MASTER]
+
+# A comma-separated list of package or module names from where C extensions may
+# be loaded. Extensions are loading into the active Python interpreter and may
+# run arbitrary code
+extension-pkg-whitelist=
+
+# Add files or directories to the blacklist. They should be base names, not
+# paths.
+ignore=CVS
+
+# Add files or directories matching the regex patterns to the blacklist. The
+# regex matches against base names, not paths.
+ignore-patterns=
+
+# Python code to execute, usually for sys.path manipulation such as
+# pygtk.require().
+#init-hook=
+
+# Use multiple processes to speed up Pylint.
+jobs=1
+
+# List of plugins (as comma separated values of python modules names) to load,
+# usually to register additional checkers.
+load-plugins=
+
+# Pickle collected data for later comparisons.
+persistent=no
+
+# Specify a configuration file.
+#rcfile=
+
+# Allow loading of arbitrary C extensions. Extensions are imported into the
+# active Python interpreter and may run arbitrary code.
+unsafe-load-any-extension=no
+
+
+[MESSAGES CONTROL]
+
+# Only show warnings with the listed confidence levels. Leave empty to show
+# all. Valid levels: HIGH, INFERENCE, INFERENCE_FAILURE, UNDEFINED
+confidence=
+
+# Disable the message, report, category or checker with the given id(s). You
+# can either give multiple identifiers separated by comma (,) or put this
+# option multiple times (only on the command line, not in the configuration
+# file where it should appear only once).You can also use "--disable=all" to
+# disable everything first and then reenable specific checks. For example, if
+# you want to run only the similarities checker, you can use "--disable=all
+# --enable=similarities". If you want to run only the classes checker, but have
+# no Warning level messages displayed, use"--disable=all --enable=classes
+# --disable=W"
+disable=print-statement,parameter-unpacking,unpacking-in-except,old-raise-syntax,backtick,long-suffix,old-ne-operator,old-octal-literal,import-star-module-level,raw-checker-failed,bad-inline-option,locally-disabled,locally-enabled,file-ignored,suppressed-message,useless-suppression,deprecated-pragma,apply-builtin,basestring-builtin,buffer-builtin,cmp-builtin,coerce-builtin,execfile-builtin,file-builtin,long-builtin,raw_input-builtin,reduce-builtin,standarderror-builtin,unicode-builtin,xrange-builtin,coerce-method,delslice-method,getslice-method,setslice-method,no-absolute-import,old-division,dict-iter-method,dict-view-method,next-method-called,metaclass-assignment,indexing-exception,raising-string,reload-builtin,oct-method,hex-method,nonzero-method,cmp-method,input-builtin,round-builtin,intern-builtin,unichr-builtin,map-builtin-not-iterating,zip-builtin-not-iterating,range-builtin-not-iterating,filter-builtin-not-iterating,using-cmp-argument,eq-without-hash,div-method,idiv-method,rdiv-method,exception-message-attribute,invalid-str-codec,sys-max-int,bad-python3-import,deprecated-string-function,deprecated-str-translate-call
+
+# Enable the message, report, category or checker with the given id(s). You can
+# either give multiple identifier separated by comma (,) or put this option
+# multiple time (only on the command line, not in the configuration file where
+# it should appear only once). See also the "--disable" option for examples.
+enable=
+
+
+[REPORTS]
+
+# Python expression which should return a note less than 10 (10 is the highest
+# note). You have access to the variables errors warning, statement which
+# respectively contain the number of errors / warnings messages and the total
+# number of statements analyzed. This is used by the global evaluation report
+# (RP0004).
+evaluation=10.0 - ((float(5 * error + warning + refactor + convention) / statement) * 10)
+
+# Template used to display messages. This is a python new-style format string
+# used to format the message information. See doc for all details
+#msg-template=
+
+# Set the output format. Available formats are text, parseable, colorized, json
+# and msvs (visual studio).You can also give a reporter class, eg
+# mypackage.mymodule.MyReporterClass.
+output-format=text
+
+# Tells whether to display a full report or only the messages
+reports=no
+
+# Activate the evaluation score.
+score=yes
+
+
+[REFACTORING]
+
+# Maximum number of nested blocks for function / method body
+max-nested-blocks=5
+
+
+[SIMILARITIES]
+
+# Ignore comments when computing similarities.
+ignore-comments=yes
+
+# Ignore docstrings when computing similarities.
+ignore-docstrings=yes
+
+# Ignore imports when computing similarities.
+ignore-imports=no
+
+# Minimum lines number of a similarity.
+min-similarity-lines=4
+
+
+[SPELLING]
+
+# Spelling dictionary name. Available dictionaries: none. To make it working
+# install python-enchant package.
+spelling-dict=
+
+# List of comma separated words that should not be checked.
+spelling-ignore-words=
+
+# A path to a file that contains private dictionary; one word per line.
+spelling-private-dict-file=
+
+# Tells whether to store unknown words to indicated private dictionary in
+# --spelling-private-dict-file option instead of raising a message.
+spelling-store-unknown-words=no
+
+
+[FORMAT]
+
+# Expected format of line ending, e.g. empty (any line ending), LF or CRLF.
+expected-line-ending-format=
+
+# Regexp for a line that is allowed to be longer than the limit.
+ignore-long-lines=^\s*(# )?<?https?://\S+>?$
+
+# Number of spaces of indent required inside a hanging  or continued line.
+indent-after-paren=4
+
+# String used as indentation unit. This is usually "    " (4 spaces) or "\t" (1
+# tab).
+indent-string='    '
+
+# Maximum number of characters on a single line.
+max-line-length=1000
+
+# Maximum number of lines in a module
+max-module-lines=1000
+
+# List of optional constructs for which whitespace checking is disabled. `dict-
+# separator` is used to allow tabulation in dicts, etc.: {1  : 1,\n222: 2}.
+# `trailing-comma` allows a space between comma and closing bracket: (a, ).
+# `empty-line` allows space-only lines.
+no-space-check=trailing-comma,dict-separator
+
+# Allow the body of a class to be on the same line as the declaration if body
+# contains single statement.
+single-line-class-stmt=no
+
+# Allow the body of an if to be on the same line as the test if there is no
+# else.
+single-line-if-stmt=no
+
+
+[TYPECHECK]
+
+# List of decorators that produce context managers, such as
+# contextlib.contextmanager. Add to this list to register other decorators that
+# produce valid context managers.
+contextmanager-decorators=contextlib.contextmanager
+
+# List of members which are set dynamically and missed by pylint inference
+# system, and so shouldn't trigger E1101 when accessed. Python regular
+# expressions are accepted.
+generated-members=
+
+# Tells whether missing members accessed in mixin class should be ignored. A
+# mixin class is detected if its name ends with "mixin" (case insensitive).
+ignore-mixin-members=yes
+
+# This flag controls whether pylint should warn about no-member and similar
+# checks whenever an opaque object is returned when inferring. The inference
+# can return multiple potential results while evaluating a Python object, but
+# some branches might not be evaluated, which results in partial inference. In
+# that case, it might be useful to still emit no-member and other checks for
+# the rest of the inferred objects.
+ignore-on-opaque-inference=no
+
+# List of class names for which member attributes should not be checked (useful
+# for classes with dynamically set attributes). This supports the use of
+# qualified names.
+ignored-classes=optparse.Values,thread._local,_thread._local
+
+# List of module names for which member attributes should not be checked
+# (useful for modules/projects where namespaces are manipulated during runtime
+# and thus existing member attributes cannot be deduced by static analysis. It
+# supports qualified module names, as well as Unix pattern matching.
+ignored-modules=
+
+# Show a hint with possible names when a member name was not found. The aspect
+# of finding the hint is based on edit distance.
+missing-member-hint=yes
+
+# The minimum edit distance a name should have in order to be considered a
+# similar match for a missing member name.
+missing-member-hint-distance=1
+
+# The total number of similar names that should be taken in consideration when
+# showing a hint for a missing member.
+missing-member-max-choices=1
+
+
+[VARIABLES]
+
+# List of additional names supposed to be defined in builtins. Remember that
+# you should avoid to define new builtins when possible.
+additional-builtins=
+
+# Tells whether unused global variables should be treated as a violation.
+allow-global-unused-variables=yes
+
+# List of strings which can identify a callback function by name. A callback
+# name must start or end with one of those strings.
+callbacks=cb_,_cb
+
+# A regular expression matching the name of dummy variables (i.e. expectedly
+# not used).
+dummy-variables-rgx=_+$|(_[a-zA-Z0-9_]*[a-zA-Z0-9]+?$)|dummy|^ignored_|^unused_
+
+# Argument names that match this expression will be ignored. Default to name
+# with leading underscore
+ignored-argument-names=_.*|^ignored_|^unused_
+
+# Tells whether we should check for unused import in __init__ files.
+init-import=no
+
+# List of qualified module names which can have objects that can redefine
+# builtins.
+redefining-builtins-modules=six.moves,future.builtins
+
+
+[MISCELLANEOUS]
+
+# List of note tags to take in consideration, separated by a comma.
+notes=FIXME,XXX,TODO,HACK
+
+
+[LOGGING]
+
+# Logging modules to check that the string format arguments are in logging
+# function parameter format
+logging-modules=logging
+
+
+[BASIC]
+
+# Naming hint for argument names
+argument-name-hint=(([a-z][a-z0-9_]{2,30})|(_[a-z0-9_]*))$
+
+# Regular expression matching correct argument names
+argument-rgx=(([a-z][a-z0-9_]{2,30})|(_[a-z0-9_]*))$
+
+# Naming hint for attribute names
+attr-name-hint=(([a-z][a-z0-9_]{2,30})|(_[a-z0-9_]*))$
+
+# Regular expression matching correct attribute names
+attr-rgx=(([a-z][a-z0-9_]{2,30})|(_[a-z0-9_]*))$
+
+# Bad variable names which should always be refused, separated by a comma
+bad-names=foo,bar,baz,toto,tutu,tata
+
+# Naming hint for class attribute names
+class-attribute-name-hint=([A-Za-z_][A-Za-z0-9_]{2,30}|(__.*__))$
+
+# Regular expression matching correct class attribute names
+class-attribute-rgx=([A-Za-z_][A-Za-z0-9_]{2,30}|(__.*__))$
+
+# Naming hint for class names
+class-name-hint=[A-Z_][a-zA-Z0-9]+$
+
+# Regular expression matching correct class names
+class-rgx=[A-Z_][a-zA-Z0-9]+$
+
+# Naming hint for constant names
+const-name-hint=(([A-Z_][A-Z0-9_]*)|(__.*__))$
+
+# Regular expression matching correct constant names
+const-rgx=(([A-Z_][A-Z0-9_]*)|(__.*__))$
+
+# Minimum line length for functions/classes that require docstrings, shorter
+# ones are exempt.
+docstring-min-length=-1
+
+# Naming hint for function names
+function-name-hint=(([a-z][a-z0-9_]{2,30})|(_[a-z0-9_]*))$
+
+# Regular expression matching correct function names
+function-rgx=(([a-z][a-z0-9_]{2,30})|(_[a-z0-9_]*))$
+
+# Good variable names which should always be accepted, separated by a comma
+good-names=i,j,k,ex,Run,_,x,y
+
+# Include a hint for the correct naming format with invalid-name
+include-naming-hint=no
+
+# Naming hint for inline iteration names
+inlinevar-name-hint=[A-Za-z_][A-Za-z0-9_]*$
+
+# Regular expression matching correct inline iteration names
+inlinevar-rgx=[A-Za-z_][A-Za-z0-9_]*$
+
+# Naming hint for method names
+method-name-hint=(([a-z][a-z0-9_]{2,30})|(_[a-z0-9_]*))$
+
+# Regular expression matching correct method names
+method-rgx=(([a-z][a-z0-9_]{2,30})|(_[a-z0-9_]*))$
+
+# Naming hint for module names
+module-name-hint=(([a-z_][a-z0-9_]*)|([A-Z][a-zA-Z0-9]+))$
+
+# Regular expression matching correct module names
+module-rgx=(([a-z_][a-z0-9_]*)|([A-Z][a-zA-Z0-9]+))$
+
+# Colon-delimited sets of names that determine each other's naming style when
+# the name regexes allow several styles.
+name-group=
+
+# Regular expression which should only match function or class names that do
+# not require a docstring.
+no-docstring-rgx=^_
+
+# List of decorators that produce properties, such as abc.abstractproperty. Add
+# to this list to register other decorators that produce valid properties.
+property-classes=abc.abstractproperty
+
+# Naming hint for variable names
+variable-name-hint=(([a-z][a-z0-9_]{2,30})|(_[a-z0-9_]*))$
+
+# Regular expression matching correct variable names
+variable-rgx=(([a-z][a-z0-9_]{2,30})|(_[a-z0-9_]*))$
+
+
+[DESIGN]
+
+# Maximum number of arguments for function / method
+max-args=8
+
+# Maximum number of attributes for a class (see R0902).
+max-attributes=7
+
+# Maximum number of boolean expressions in a if statement
+max-bool-expr=5
+
+# Maximum number of branch for function / method body
+max-branches=16
+
+# Maximum number of locals for function / method body
+max-locals=15
+
+# Maximum number of parents for a class (see R0901).
+max-parents=7
+
+# Maximum number of public methods for a class (see R0904).
+max-public-methods=20
+
+# Maximum number of return / yield for function / method body
+max-returns=6
+
+# Maximum number of statements in function / method body
+max-statements=50
+
+# Minimum number of public methods for a class (see R0903).
+min-public-methods=2
+
+
+[IMPORTS]
+
+# Allow wildcard imports from modules that define __all__.
+allow-wildcard-with-all=no
+
+# Analyse import fallback blocks. This can be used to support both Python 2 and
+# 3 compatible code, which means that the block might have code that exists
+# only in one or another interpreter, leading to false positives when analysed.
+analyse-fallback-blocks=no
+
+# Deprecated modules which should not be used, separated by a comma
+deprecated-modules=regsub,TERMIOS,Bastion,rexec
+
+# Create a graph of external dependencies in the given file (report RP0402 must
+# not be disabled)
+ext-import-graph=
+
+# Create a graph of every (i.e. internal and external) dependencies in the
+# given file (report RP0402 must not be disabled)
+import-graph=
+
+# Create a graph of internal dependencies in the given file (report RP0402 must
+# not be disabled)
+int-import-graph=
+
+# Force import order to recognize a module as part of the standard
+# compatibility libraries.
+known-standard-library=
+
+# Force import order to recognize a module as part of a third party library.
+known-third-party=enchant
+
+
+[CLASSES]
+
+# List of method names used to declare (i.e. assign) instance attributes.
+defining-attr-methods=__init__,__new__,setUp
+
+# List of member names, which should be excluded from the protected access
+# warning.
+exclude-protected=_asdict,_fields,_replace,_source,_make
+
+# List of valid names for the first argument in a class method.
+valid-classmethod-first-arg=cls
+
+# List of valid names for the first argument in a metaclass class method.
+valid-metaclass-classmethod-first-arg=mcs
+
+
+[EXCEPTIONS]
+
+# Exceptions that will emit a warning when being caught. Defaults to
+# "Exception"
+overgeneral-exceptions=Exception
diff --git a/ci/static_checker.sh b/ci/static_checker.sh
new file mode 100755
index 0000000000000000000000000000000000000000..5915cd589da382bd5b9ece9f5d2c558f16f5f7e2
--- /dev/null
+++ b/ci/static_checker.sh
@@ -0,0 +1,20 @@
+#!/usr/bin/env bash
+echo "===========================  Install static checker ============================"
+conda install pylint pycodestyle > tmp.txt && echo 'static code checker installed'
+pip install diff_cover > tmp.txt && echo 'diff code checker installed'
+
+echo "============================== Pylint check FULL ==============================="
+pylint --rcfile=ci/pylintrc --msg-template="{path}:{line}: [{msg_id}({symbol}), {obj}] {msg}" analysis > pylint_report.txt && (exit 0)
+tail -n 3 pylint_report.txt
+
+echo "============================== Pylint check DIFF ==============================="
+diff-quality --violations=pylint --fail-under=95 pylint_report.txt --options="--rcfile=ci/pylintrc"
+
+echo "============================= Codestyle check FULL ============================="
+pycodestyle --max-line-length=1000 analysis > report_pycodestyle.txt || (exit 0)
+pycodestyle --statistics -qq --max-line-length=100 analysis || (exit 0)
+
+echo "============================ Codestyle check DIFF =============================="
+diff-quality --violations=pycodestyle --fail-under=95 report_pycodestyle.txt  --options="--max-line-length=100"
+
+echo "===========================  Finished static checks ============================"
diff --git a/ci/test_runner.sh b/ci/test_runner.sh
new file mode 100755
index 0000000000000000000000000000000000000000..88048d4d21710e056b32c3cacf6be32b89324821
--- /dev/null
+++ b/ci/test_runner.sh
@@ -0,0 +1,15 @@
+#!/usr/bin/env bash
+#   install test utilities
+echo "============================ Install test utilities ============================"
+conda install pytest coverage > tmp.txt && echo 'test utils installed'
+pip install diff_cover > tmp.txt && echo 'diff code checker installed'
+
+#    run tests
+echo "======================= Running tests with coverage FULL ======================="
+coverage run -m pytest -k "not test_load_with_weights" tests/ # excluding a test in test_data.py
+coverage report analysis/*/*.py
+coverage xml analysis/*/*.py
+echo "================================ Coverage DIFF ================================="
+diff-cover coverage.xml | tail -n 5
+
+echo "=============================== Finished tests ================================="
diff --git a/ci/testbuild_docs.sh b/ci/testbuild_docs.sh
new file mode 100755
index 0000000000000000000000000000000000000000..19c1ba275dfecede4cd7ed075aae8bccba4a8686
--- /dev/null
+++ b/ci/testbuild_docs.sh
@@ -0,0 +1,7 @@
+#!/usr/bin/env bash
+#    test build docs
+echo "============================ Building docs for test ============================"
+conda install sphinx sphinx_rtd_theme > tmp.txt && echo 'test utils installed'
+bash docs/make_docs.sh 2>&1 | tail -n 11
+echo "======================= Finished building docs for test ========================"
+
diff --git a/tests/test_data.py b/tests/test_data.py
index 313be7724aade995204ffa1bef54a1f11f9f9629..dff107dcf2db5b7386b3888e8de6793466d08307 100644
--- a/tests/test_data.py
+++ b/tests/test_data.py
@@ -71,6 +71,7 @@ def test_load_with_weights(pandas_weights):
                          'output-format': 'root',
                          'input-type': 'pandas',
                          'weights-to-normalize': ['half', 'quarter', 'asym']})
+
         if not data.isWeighted():
             return False
         # Correct normalization
@@ -81,5 +82,4 @@ def test_load_with_weights(pandas_weights):
         data.get(999)
         assert data.weight() == 0.6666666666666666
 
-
 # EOF
diff --git a/tests/test_syst.py b/tests/test_syst.py
index a8ad43bc41af979d98d68f86ca3eb98fa07367ef..0c8d4c4e164fa78b4af10fb2d4ca81cf415505be 100644
--- a/tests/test_syst.py
+++ b/tests/test_syst.py
@@ -25,14 +25,14 @@ def test_factory_split(factory, factory_with_yield):
         pass
     # Manual yield
     syst_fac = SystematicToys(factory, {'yield': 100})
-    assert syst_fac._gen_pdfs.keys() == [None]
+    assert list(syst_fac._gen_pdfs.keys()) == [None]
     assert len(syst_fac._gen_pdfs[None]) == 1
     assert syst_fac._gen_pdfs[None][0].expectedEvents(
         list_to_rooargset(
             factory.get_observables())) == 100
     # Yield from config
     syst_fac = SystematicToys(factory_with_yield)
-    assert syst_fac._gen_pdfs.keys() == [None]
+    assert list(syst_fac._gen_pdfs.keys()) == [None]
     assert len(syst_fac._gen_pdfs[None]) == 1
     assert syst_fac._gen_pdfs[None][0].expectedEvents(
         list_to_rooargset(
@@ -43,7 +43,7 @@ def test_factory_split(factory, factory_with_yield):
 def test_prodfactory_split(prod_factory):
     """Test function splitting is done properly."""
     syst_fac = SystematicToys(prod_factory)
-    assert syst_fac._gen_pdfs.keys() == [None]
+    assert list(syst_fac._gen_pdfs.keys()) == [None]
     assert len(syst_fac._gen_pdfs[None]) == 1
     assert syst_fac._gen_pdfs[None][0].expectedEvents(
         list_to_rooargset(
@@ -55,7 +55,7 @@ def test_sumfactory_factory_split(sum_factory, sum_factory_frac):
     """Test function splitting is done properly."""
     # With yields
     syst_fac = SystematicToys(sum_factory)
-    assert syst_fac._gen_pdfs.keys() == [None]
+    assert list(syst_fac._gen_pdfs.keys()) == [None]
     assert len(syst_fac._gen_pdfs[None]) == 2
     assert syst_fac._gen_pdfs[None][0].expectedEvents(
         list_to_rooargset(
@@ -65,7 +65,7 @@ def test_sumfactory_factory_split(sum_factory, sum_factory_frac):
             sum_factory.get_observables())) == 999
     # With fraction
     syst_fac = SystematicToys(sum_factory_frac, {'yield': 100})
-    assert syst_fac._gen_pdfs.keys() == [None]
+    assert list(syst_fac._gen_pdfs.keys()) == [None]
     assert len(syst_fac._gen_pdfs[None]) == 1
     assert syst_fac._gen_pdfs[None][0].expectedEvents(
         list_to_rooargset(
@@ -77,7 +77,7 @@ def test_simfactory_factory_split(sim_factory):
     """Test function splitting is done properly."""
     # With yields
     syst_fac = SystematicToys(sim_factory)
-    assert syst_fac._gen_pdfs.keys() == ['label1', 'label2']
+    assert list(syst_fac._gen_pdfs.keys()) == ['label1', 'label2']
     assert len(syst_fac._gen_pdfs['label1']) == 2
     assert syst_fac._gen_pdfs['label1'][0].expectedEvents(
         list_to_rooargset(