diff --git a/bonobo/commands/init.py b/bonobo/commands/init.py
index 948f747..e69156c 100644
--- a/bonobo/commands/init.py
+++ b/bonobo/commands/init.py
@@ -1,3 +1,5 @@
+import os
+
 def execute(name, branch):
     try:
         from cookiecutter.main import cookiecutter
@@ -6,11 +8,17 @@ def execute(name, branch):
             'You must install "cookiecutter" to use this command.\n\n $ pip install cookiecutter\n'
         ) from exc
 
+    overwrite_if_exists = False
+    project_path = os.path.join(os.getcwd(), name)
+    if os.path.isdir(project_path) and not os.listdir(project_path):
+        overwrite_if_exists = True
+
     return cookiecutter(
         'https://github.com/python-bonobo/cookiecutter-bonobo.git',
         extra_context={'name': name},
         no_input=True,
-        checkout=branch
+        checkout=branch,
+        overwrite_if_exists=overwrite_if_exists
     )
 
 
diff --git a/bonobo/examples/tutorials/tut02e02_write.py b/bonobo/examples/tutorials/tut02e02_write.py
index e5a8445..c4b065d 100644
--- a/bonobo/examples/tutorials/tut02e02_write.py
+++ b/bonobo/examples/tutorials/tut02e02_write.py
@@ -2,14 +2,14 @@ import bonobo
 
 
 def split_one(line):
-    return line.split(', ', 1)
+    return dict(zip(("name", "address"), line.split(', ', 1)))
 
 
 graph = bonobo.Graph(
     bonobo.FileReader('coffeeshops.txt'),
     split_one,
     bonobo.JsonWriter(
-        'coffeeshops.json', fs='fs.output', ioformat='arg0'
+        'coffeeshops.json', fs='fs.output'
     ),
 )
 
diff --git a/bonobo/examples/tutorials/tut02e03_writeasmap.py b/bonobo/examples/tutorials/tut02e03_writeasmap.py
index e234f22..c7c7711 100644
--- a/bonobo/examples/tutorials/tut02e03_writeasmap.py
+++ b/bonobo/examples/tutorials/tut02e03_writeasmap.py
@@ -11,7 +11,7 @@ def split_one_to_map(line):
 class MyJsonWriter(bonobo.JsonWriter):
     prefix, suffix = '{', '}'
 
-    def write(self, fs, file, lineno, row):
+    def write(self, fs, file, lineno, **row):
         return bonobo.FileWriter.write(
             self, fs, file, lineno, json.dumps(row)[1:-1]
         )
@@ -20,7 +20,7 @@ class MyJsonWriter(bonobo.JsonWriter):
 graph = bonobo.Graph(
     bonobo.FileReader('coffeeshops.txt'),
     split_one_to_map,
-    MyJsonWriter('coffeeshops.json', fs='fs.output', ioformat='arg0'),
+    MyJsonWriter('coffeeshops.json', fs='fs.output'),
 )
 
 
diff --git a/docs/tutorial/tut01.rst b/docs/tutorial/tut01.rst
index d6aa604..3d6f9eb 100644
--- a/docs/tutorial/tut01.rst
+++ b/docs/tutorial/tut01.rst
@@ -105,6 +105,9 @@ To do this, it needs to know what data-flow you want to achieve, and you'll use
     The `if __name__ == '__main__':` section is not required, unless you want to run it directly using the python
     interpreter.
 
+    The name of the `graph` variable is arbitrary, but this variable must be global and available unconditionally.
+    Do not put it in its own function or in the `if __name__ == '__main__':` section.
+
 
 Execute the job
 :::::::::::::::
diff --git a/tests/test_commands.py b/tests/test_commands.py
index e467bb3..a96634c 100644
--- a/tests/test_commands.py
+++ b/tests/test_commands.py
@@ -8,18 +8,24 @@ from unittest.mock import patch
 
 import pkg_resources
 import pytest
+from cookiecutter.exceptions import OutputDirExistsException
 
 from bonobo import __main__, __version__, get_examples_path
 from bonobo.commands import entrypoint
+from bonobo.commands.run import DEFAULT_GRAPH_FILENAMES
 
 
 def runner(f):
     @functools.wraps(f)
-    def wrapped_runner(*args):
+    def wrapped_runner(*args, catch_errors=False):
         with redirect_stdout(io.StringIO()) as stdout, redirect_stderr(io.StringIO()) as stderr:
             try:
                 f(list(args))
             except BaseException as exc:
+                if not catch_errors:
+                    raise
+                elif isinstance(catch_errors, BaseException) and not isinstance(exc, catch_errors):
+                    raise
                 return stdout.getvalue(), stderr.getvalue(), exc
         return stdout.getvalue(), stderr.getvalue()
 
@@ -40,6 +46,7 @@ def runner_module(args):
 
 
 all_runners = pytest.mark.parametrize('runner', [runner_entrypoint, runner_module])
+single_runner = pytest.mark.parametrize('runner', [runner_module])
 
 
 def test_entrypoint():
@@ -59,11 +66,41 @@ def test_entrypoint():
 
 @all_runners
 def test_no_command(runner):
-    _, err, exc = runner()
+    _, err, exc = runner(catch_errors=True)
     assert type(exc) == SystemExit
     assert 'error: the following arguments are required: command' in err
 
 
+@all_runners
+def test_init(runner, tmpdir):
+    name = 'project'
+    tmpdir.chdir()
+    runner('init', name)
+    assert os.path.isdir(name)
+    assert set(os.listdir(name)) & set(DEFAULT_GRAPH_FILENAMES)
+
+@single_runner
+def test_init_in_empty_then_nonempty_directory(runner, tmpdir):
+    name = 'project'
+    tmpdir.chdir()
+    os.mkdir(name)
+
+    # run in empty dir
+    runner('init', name)
+    assert set(os.listdir(name)) & set(DEFAULT_GRAPH_FILENAMES)
+
+    # run in non empty dir
+    with pytest.raises(OutputDirExistsException):
+        runner('init', name)
+
+
+@single_runner
+def test_init_within_empty_directory(runner, tmpdir):
+    tmpdir.chdir()
+    runner('init', '.')
+    assert set(os.listdir()) & set(DEFAULT_GRAPH_FILENAMES)
+
+
 @all_runners
 def test_run(runner):
     out, err = runner('run', '--quiet', get_examples_path('types/strings.py'))