From 0f5fb7ed05c7911bbfe1583491f735c205453c34 Mon Sep 17 00:00:00 2001
From: Daniel Hahler <git@thequod.de>
Date: Wed, 29 Nov 2017 00:54:14 +0100
Subject: [PATCH 1/2] Fix ZeroDivisionError with 0 collected tests

This can easily happen with pytest-testmon.
---
 _pytest/terminal.py | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/_pytest/terminal.py b/_pytest/terminal.py
index 8538ee6aa..c5cbe14a1 100644
--- a/_pytest/terminal.py
+++ b/_pytest/terminal.py
@@ -313,8 +313,11 @@ class TerminalReporter:
     _PROGRESS_LENGTH = len(' [100%]')
 
     def _get_progress_information_message(self):
-        progress = self._progress_items_reported * 100 // self._session.testscollected
-        return ' [{:3d}%]'.format(progress)
+        collected = self._session.testscollected
+        if collected:
+            progress = self._progress_items_reported * 100 // collected
+            return ' [{:3d}%]'.format(progress)
+        return ' [100%]'
 
     def _write_progress_information_filling_space(self):
         if not self._show_progress_info:

From 6bbd7410397fc3ea95b48cf38a3d8070ebf80fb7 Mon Sep 17 00:00:00 2001
From: Bruno Oliveira <nicoddemus@gmail.com>
Date: Tue, 28 Nov 2017 22:42:52 -0200
Subject: [PATCH 2/2] Add test for #2971

---
 changelog/2971.bugfix    |  1 +
 testing/test_terminal.py | 18 ++++++++++++++++++
 2 files changed, 19 insertions(+)
 create mode 100644 changelog/2971.bugfix

diff --git a/changelog/2971.bugfix b/changelog/2971.bugfix
new file mode 100644
index 000000000..36684e8c8
--- /dev/null
+++ b/changelog/2971.bugfix
@@ -0,0 +1 @@
+Fix ``ZeroDivisionError`` when using the ``testmon`` plugin when no tests were actually collected.
diff --git a/testing/test_terminal.py b/testing/test_terminal.py
index 98a8ca121..97c2f71fb 100644
--- a/testing/test_terminal.py
+++ b/testing/test_terminal.py
@@ -988,6 +988,24 @@ class TestProgress:
             """,
         )
 
+    def test_zero_tests_collected(self, testdir):
+        """Some plugins (testmon for example) might issue pytest_runtest_logreport without any tests being
+        actually collected (#2971)."""
+        testdir.makeconftest("""
+        def pytest_collection_modifyitems(items, config):
+            from _pytest.runner import CollectReport
+            for node_id in ('nodeid1', 'nodeid2'):
+                rep = CollectReport(node_id, 'passed', None, None)
+                rep.when = 'passed'
+                rep.duration = 0.1
+                config.hook.pytest_runtest_logreport(report=rep)
+        """)
+        output = testdir.runpytest()
+        assert 'ZeroDivisionError' not in output.stdout.str()
+        output.stdout.fnmatch_lines([
+            '=* 2 passed in *=',
+        ])
+
     def test_normal(self, many_tests_file, testdir):
         output = testdir.runpytest()
         output.stdout.re_match_lines([