diff --git a/prototype/Doubt.xcodeproj/project.pbxproj b/prototype/Doubt.xcodeproj/project.pbxproj
index 9c5e627c8..909ae7bbc 100644
--- a/prototype/Doubt.xcodeproj/project.pbxproj
+++ b/prototype/Doubt.xcodeproj/project.pbxproj
@@ -11,6 +11,7 @@
 		D40B89C81BC439000078E098 /* Assertions.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = D40B89C71BC439000078E098 /* Assertions.framework */; };
 		D40D72541BCEEB1F001B7A9E /* AlgorithmTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = D40D72531BCEEB1F001B7A9E /* AlgorithmTests.swift */; settings = {ASSET_TAGS = (); }; };
 		D40D725A1BD15321001B7A9E /* SwiftCheck.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = D40D72591BD15321001B7A9E /* SwiftCheck.framework */; };
+		D40D725C1BD15417001B7A9E /* RangedTerm.swift in Sources */ = {isa = PBXBuildFile; fileRef = D40D725B1BD15417001B7A9E /* RangedTerm.swift */; settings = {ASSET_TAGS = (); }; };
 		D42F096B1BCCC41600B95610 /* Either.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = D42F09671BCCC41600B95610 /* Either.framework */; };
 		D42F096C1BCCC41600B95610 /* Memo.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = D42F09681BCCC41600B95610 /* Memo.framework */; };
 		D42F096D1BCCC41600B95610 /* Prelude.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = D42F09691BCCC41600B95610 /* Prelude.framework */; };
@@ -60,6 +61,7 @@
 		D40B89C71BC439000078E098 /* Assertions.framework */ = {isa = PBXFileReference; lastKnownFileType = wrapper.framework; path = Assertions.framework; sourceTree = BUILT_PRODUCTS_DIR; };
 		D40D72531BCEEB1F001B7A9E /* AlgorithmTests.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = AlgorithmTests.swift; sourceTree = "<group>"; };
 		D40D72591BD15321001B7A9E /* SwiftCheck.framework */ = {isa = PBXFileReference; lastKnownFileType = wrapper.framework; path = SwiftCheck.framework; sourceTree = BUILT_PRODUCTS_DIR; };
+		D40D725B1BD15417001B7A9E /* RangedTerm.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = RangedTerm.swift; sourceTree = "<group>"; };
 		D42F09671BCCC41600B95610 /* Either.framework */ = {isa = PBXFileReference; lastKnownFileType = wrapper.framework; path = Either.framework; sourceTree = BUILT_PRODUCTS_DIR; };
 		D42F09681BCCC41600B95610 /* Memo.framework */ = {isa = PBXFileReference; lastKnownFileType = wrapper.framework; path = Memo.framework; sourceTree = BUILT_PRODUCTS_DIR; };
 		D42F09691BCCC41600B95610 /* Prelude.framework */ = {isa = PBXFileReference; lastKnownFileType = wrapper.framework; path = Prelude.framework; sourceTree = BUILT_PRODUCTS_DIR; };
@@ -194,6 +196,7 @@
 			children = (
 				D432D4701BA9AC0B00F3FABC /* SESTests.swift */,
 				D40D72531BCEEB1F001B7A9E /* AlgorithmTests.swift */,
+				D40D725B1BD15417001B7A9E /* RangedTerm.swift */,
 				D4AAE5141B5AE22E004E581F /* Info.plist */,
 				D40B89C71BC439000078E098 /* Assertions.framework */,
 				D40D72591BD15321001B7A9E /* SwiftCheck.framework */,
@@ -371,6 +374,7 @@
 			files = (
 				D432D4711BA9AC0B00F3FABC /* SESTests.swift in Sources */,
 				D40D72541BCEEB1F001B7A9E /* AlgorithmTests.swift in Sources */,
+				D40D725C1BD15417001B7A9E /* RangedTerm.swift in Sources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};
diff --git a/prototype/DoubtTests/RangedTerm.swift b/prototype/DoubtTests/RangedTerm.swift
new file mode 100644
index 000000000..2fa762c83
--- /dev/null
+++ b/prototype/DoubtTests/RangedTerm.swift
@@ -0,0 +1,6 @@
+struct RangedTerm {
+	let term: Cofree<String, Range<String.Index>>
+}
+
+
+@testable import Doubt