From 43b9b864af176198f67b49e348d488f531599863 Mon Sep 17 00:00:00 2001
From: Phil Elson <philip.elson@cern.ch>
Date: Fri, 6 Aug 2021 09:29:12 +0200
Subject: [PATCH] Improve the testing of ConcentrationModel.last_state_change

---
 cara/models.py                                |  2 +-
 cara/tests/models/test_concentration_model.py | 26 +++++++++++++++++++
 2 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/cara/models.py b/cara/models.py
index 2f7dcbd7..80f993d5 100644
--- a/cara/models.py
+++ b/cara/models.py
@@ -775,7 +775,7 @@ class ConcentrationModel:
 
     def last_state_change(self, time: float) -> float:
         """
-        Find the most recent state change.
+        Find the most recent/previous state change.
 
         """
         for change_time in self.state_change_times()[::-1]:
diff --git a/cara/tests/models/test_concentration_model.py b/cara/tests/models/test_concentration_model.py
index a036d350..9470dd56 100644
--- a/cara/tests/models/test_concentration_model.py
+++ b/cara/tests/models/test_concentration_model.py
@@ -68,6 +68,32 @@ def simple_conc_model():
     )
 
 
+@pytest.mark.parametrize(
+    "time, expected_last_state_change", [
+        [0., 0],
+        [1., 0],
+        [1.05, 1.],
+        [1.1, 1.],
+        [1.11, 1.1],
+        [1.999, 1.1],
+        [1.9991, 1.999],
+        [2., 1.999],
+        [2.1, 2],
+        [3., 2],
+    ]
+)
+def test_last_state_change_time(
+        simple_conc_model: models.ConcentrationModel,
+        time,
+        expected_last_state_change,
+):
+    assert simple_conc_model.last_state_change(float(time)) == expected_last_state_change
+
+
+def test_last_state_change_time_out_of_range(simple_conc_model: models.ConcentrationModel):
+    assert simple_conc_model.last_state_change(3.1) == 3.0
+
+
 @pytest.mark.parametrize(
     "time, expected_next_state_change", [
         [0, 0],