diff --git a/tests/test_materials.py b/tests/test_materials.py
index 858d540..af728f6 100644
--- a/tests/test_materials.py
+++ b/tests/test_materials.py
@@ -1,11 +1,14 @@
 import fractions
+import typing
 import unittest
 
 from elite_engineering import materials
 
 
 class TradeCalculationTests(unittest.TestCase):
-    def format_ratio(self, ratio: fractions.Fraction) -> str:
+    def format_ratio(self, ratio: typing.Optional[fractions.Fraction]) -> str:
+        if not ratio:
+            return "-"
         return "{} → {}".format(ratio.numerator, ratio.denominator)
 
     def test_same_category_exchange(self) -> None:
@@ -19,16 +22,15 @@ class TradeCalculationTests(unittest.TestCase):
 
         actual = [
             [
-                materials.Material(
-                    "name", materials.MaterialType.raw, "category", grade_in
-                )
-                .trade_ratio(
+                self.format_ratio(
                     materials.Material(
-                        "name", materials.MaterialType.raw, "category", grade_out
+                        "name", materials.MaterialType.raw, "category", grade_in
+                    ).trade_ratio(
+                        materials.Material(
+                            "name", materials.MaterialType.raw, "category", grade_out
+                        )
                     )
                 )
-                .map(self.format_ratio)
-                .value_or("-")
                 for grade_in in [1, 2, 3, 4, 5]
             ]
             for grade_out in [1, 2, 3, 4, 5]
@@ -47,16 +49,15 @@ class TradeCalculationTests(unittest.TestCase):
 
         actual = [
             [
-                materials.Material(
-                    "name", materials.MaterialType.raw, "category", grade_in
-                )
-                .trade_ratio(
+                self.format_ratio(
                     materials.Material(
-                        "name", materials.MaterialType.raw, "other", grade_out
+                        "name", materials.MaterialType.raw, "category", grade_in
+                    ).trade_ratio(
+                        materials.Material(
+                            "name", materials.MaterialType.raw, "other", grade_out
+                        )
                     )
                 )
-                .map(self.format_ratio)
-                .value_or("-")
                 for grade_in in [1, 2, 3, 4, 5]
             ]
             for grade_out in [1, 2, 3, 4, 5]
@@ -75,16 +76,15 @@ class TradeCalculationTests(unittest.TestCase):
 
         actual = [
             [
-                materials.Material(
-                    "name", materials.MaterialType.raw, "category", grade_in
-                )
-                .trade_ratio(
+                self.format_ratio(
                     materials.Material(
-                        "name", materials.MaterialType.encoded, "other", grade_out
+                        "name", materials.MaterialType.raw, "category", grade_in
+                    ).trade_ratio(
+                        materials.Material(
+                            "name", materials.MaterialType.encoded, "other", grade_out
+                        )
                     )
                 )
-                .map(self.format_ratio)
-                .value_or("-")
                 for grade_in in [1, 2, 3, 4, 5]
             ]
             for grade_out in [1, 2, 3, 4, 5]
diff --git a/tests/test_trade.py b/tests/test_trade.py
index 6851789..c44ae39 100644
--- a/tests/test_trade.py
+++ b/tests/test_trade.py
@@ -1,11 +1,14 @@
 import fractions
+import typing
 import unittest
 
 from elite_engineering import trade
 
 
 class TradeCalculationTests(unittest.TestCase):
-    def format_ratio(self, ratio: fractions.Fraction) -> str:
+    def format_ratio(self, ratio: typing.Optional[fractions.Fraction]) -> str:
+        if not ratio:
+            return "-"
         return "{} → {}".format(ratio.numerator, ratio.denominator)
 
     def test_same_category_exchange(self) -> None:
@@ -19,9 +22,9 @@ class TradeCalculationTests(unittest.TestCase):
 
         actual = [
             [
-                trade.ratio(grade_in, grade_out, across_categories=False)
-                .map(self.format_ratio)
-                .value_or("-")
+                self.format_ratio(
+                    trade.ratio(grade_in, grade_out, across_categories=False)
+                )
                 for grade_in in [1, 2, 3, 4, 5]
             ]
             for grade_out in [1, 2, 3, 4, 5]
@@ -40,9 +43,9 @@ class TradeCalculationTests(unittest.TestCase):
 
         actual = [
             [
-                trade.ratio(grade_in, grade_out, across_categories=True)
-                .map(self.format_ratio)
-                .value_or("-")
+                self.format_ratio(
+                    trade.ratio(grade_in, grade_out, across_categories=True)
+                )
                 for grade_in in [1, 2, 3, 4, 5]
             ]
             for grade_out in [1, 2, 3, 4, 5]