diff --git a/tests/test_catmath.py b/tests/test_catmath.py
index ced6358..2a29273 100644
--- a/tests/test_catmath.py
+++ b/tests/test_catmath.py
@@ -2,18 +2,21 @@
 
 
 def test__cat_years_to_hooman_years__middle_age__succeeds():
-    assert True
+    cat_years = 10
+    human_years = catmath.cat_years_to_hooman_years(cat_years)
+    assert human_years == 50
 
 
 def test__cat_years_to_hooman_years__less_than_one_year__succeeds():
-    assert True
+    cat_years = 0.5
+    human_years = catmath.cat_years_to_hooman_years(cat_years)
+    assert human_years == 2.5
 
 
 def test__cat_years_to_hooman_years__0__returns_0():
-    assert True
+    assert catmath.cat_years_to_hooman_years(0) == 0
 
 
 # BONUS MATERIAL FOR STEP 2
-
 def test__is_cat_leap_year__succeeds():
     assert catmath.is_cat_leap_year(2016) is True
diff --git a/tests/test_cattery.py b/tests/test_cattery.py
index b36692c..3ecd863 100644
--- a/tests/test_cattery.py
+++ b/tests/test_cattery.py
@@ -6,34 +6,34 @@
 ###########################################################################
 # add_cats
 ###########################################################################
+@pytest.fixture(scope='function')
+def cattery_client():
+    return cattery.Cattery()
 
-def test__add_cats__succeeds():
-    c = cattery.Cattery()
-    c.add_cats(["Fluffy", "Snookums"])
-    assert c.cats == ["Fluffy", "Snookums"]
-    assert c.num_cats == 2
+
+def test__add_cats__succeeds(cattery_client):
+    cattery_client.add_cats(["Fluffy", "Snookums"])
+    assert cattery_client.cats == ["Fluffy", "Snookums"]
+    assert cattery_client.num_cats == 2
 
 
 ###########################################################################
 # remove_cat
 ###########################################################################
 
-def test__remove_cat__succeeds():
-    c = cattery.Cattery()
-    c.add_cats(["Fluffy", "Junior"])
-    c.remove_cat("Fluffy")
-    assert c.cats == ["Junior"]
-    assert c.num_cats == 1
+def test__remove_cat__succeeds(cattery_client):
+    cattery_client.add_cats(["Fluffy", "Junior"])
+    cattery_client.remove_cat("Fluffy")
+    assert cattery_client.cats == ["Junior"]
+    assert cattery_client.num_cats == 1
 
 
-def test__remove_cat__no_cats__fails():
-    c = cattery.Cattery()
+def test__remove_cat__no_cats__fails(cattery_client):
     with pytest.raises(cattery.CatNotFound):
-        c.remove_cat("Fluffles")
+        cattery_client.remove_cat("Fluffles")
 
 
-def test__remove_cat__cat_not_in_cattery__fails():
-    c = cattery.Cattery()
-    c.add_cats(["Fluffy"])
+def test__remove_cat__cat_not_in_cattery__fails(cattery_client):
+    cattery_client.add_cats(["Fluffy"])
     with pytest.raises(cattery.CatNotFound):
-        c.remove_cat("Snookums")
+        cattery_client.remove_cat("Snookums")
diff --git a/tests/test_safecatmath.py b/tests/test_safecatmath.py
index 3f85a35..bf15d68 100644
--- a/tests/test_safecatmath.py
+++ b/tests/test_safecatmath.py
@@ -1,6 +1,7 @@
-# import pytest
+import pytest
 
 from catinabox import safecatmath
+from catinabox.safecatmath import InvalidAge
 
 
 def test__cat_years_to_hooman_years__middle_age__succeeds():
@@ -19,17 +20,20 @@ def test__cat_years_to_hooman_years__0__returns_0():
 
 
 def test__cat_years_to_hooman_years__less_0__raises():
-    assert True
+    with pytest.raises(InvalidAge):
+        safecatmath.cat_years_to_hooman_years(-1)
 
 
 def test__cat_years_to_hooman_years__older_than_1000__raises():
-    assert True
+    with pytest.raises(InvalidAge):
+        safecatmath.cat_years_to_hooman_years(1001)
 
 
 def test__cat_years_to_hooman_years__string__raises():
-    assert True
+    with pytest.raises(InvalidAge):
+        safecatmath.cat_years_to_hooman_years('str')
 
 
 def test__cat_years_to_hooman_years__nan__raises():
-    # hooman_age = float('nan')
-    assert True
+    with pytest.raises(InvalidAge):
+        safecatmath.cat_years_to_hooman_years(float('nan'))