Add test for fpn

Author: qubvel

tests/models/test_fpn.py

@@ -1,6 +1,30 @@
+import segmentation_models_pytorch as smp
+
 from tests.models import base
 
 
 class TestFpnModel(base.BaseModelTester):
     test_model_type = "fpn"
     files_for_diff = [r"decoders/fpn/", r"base/"]
+
+    def test_interpolation(self):
+
+        # test bilinear
+        model_1 = smp.create_model(
+            self.test_model_type,
+            self.test_encoder_name,
+            decoder_interpolation="bilinear",
+        )
+        assert model_1.decoder.p2.interpolation_mode == "bilinear"
+        assert model_1.decoder.p3.interpolation_mode == "bilinear"
+        assert model_1.decoder.p4.interpolation_mode == "bilinear"
+
+        # test bicubic
+        model_2 = smp.create_model(
+            self.test_model_type,
+            self.test_encoder_name,
+            decoder_interpolation="bicubic",
+        )
+        assert model_2.decoder.p2.interpolation_mode == "bicubic"
+        assert model_2.decoder.p3.interpolation_mode == "bicubic"
+        assert model_2.decoder.p4.interpolation_mode == "bicubic"