1 files changed, 19 insertions, 0 deletions
diff --git a/src/test/java/org/shedlang/compiler/sources/FileFragmentSourceTests.java b/src/test/java/org/shedlang/compiler/sources/FileFragmentSourceTests.java
index 534f10c5..ce43303c 100644
--- a/src/test/java/org/shedlang/compiler/sources/FileFragmentSourceTests.java
+++ b/src/test/java/org/shedlang/compiler/sources/FileFragmentSourceTests.java
@@ -1,6 +1,7 @@
 package org.shedlang.compiler.sources;
 
 import org.junit.jupiter.api.DynamicTest;
+import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.TestFactory;
 
 import java.util.List;
@@ -107,4 +108,22 @@ public class FileFragmentSourceTests {
             assertThat(source.describe(), equalTo(testCase.expectedContext));
         })).collect(Collectors.toList());
     }
+
+    @Test
+    public void atReturnsSubsectionOfCompleteSource() {
+        var source = FileFragmentSource.file("<filename>", "abcdefg");
+
+        var fragment = source.at(2, 5);
+
+        assertThat(fragment, equalTo(new FileFragmentSource("<filename>", "abcdefg", 2, 5)));
+    }
+
+    @Test
+    public void atReturnsSubsectionOfIncompleteSource() {
+        var source = FileFragmentSource.file("<filename>", "abcdefg");
+
+        var fragment = source.at(1, 6).at(1, 4);
+
+        assertThat(fragment, equalTo(new FileFragmentSource("<filename>", "abcdefg", 2, 5)));
+    }
 }