diff --git a/src/runtimes/dotnet/extension.rs b/src/runtimes/dotnet/extension.rs
index 7c8a31ca..7bd08f76 100644
--- a/src/runtimes/dotnet/extension.rs
+++ b/src/runtimes/dotnet/extension.rs
@@ -238,7 +238,12 @@ mod tests {
         .unwrap();
         let dotnet = fm.runtimes.as_ref().unwrap().dotnet.as_ref().unwrap();
         let ext = DotnetExtension::new(dotnet.clone());
-        assert!(ext.declarations(&ctx_from(&fm)).is_err());
+        let err = ext.declarations(&ctx_from(&fm)).unwrap_err();
+        assert!(
+            err.to_string().contains("ADO expression"),
+            "expected injection error in feed-url, got: {err}"
+        );
+        assert!(err.to_string().contains("runtimes.dotnet.feed-url"), "got: {err}");
     }
 
     #[test]
@@ -249,7 +254,12 @@ mod tests {
         .unwrap();
         let dotnet = fm.runtimes.as_ref().unwrap().dotnet.as_ref().unwrap();
         let ext = DotnetExtension::new(dotnet.clone());
-        assert!(ext.declarations(&ctx_from(&fm)).is_err());
+        let err = ext.declarations(&ctx_from(&fm)).unwrap_err();
+        assert!(
+            err.to_string().contains("ADO expression"),
+            "expected injection error, got: {err}"
+        );
+        assert!(err.to_string().contains("runtimes.dotnet.version"), "got: {err}");
     }
 
     #[test]
diff --git a/src/runtimes/node/extension.rs b/src/runtimes/node/extension.rs
index 86e6186c..98eeb6a3 100644
--- a/src/runtimes/node/extension.rs
+++ b/src/runtimes/node/extension.rs
@@ -207,7 +207,12 @@ mod tests {
         .unwrap();
         let node = fm.runtimes.as_ref().unwrap().node.as_ref().unwrap();
         let ext = NodeExtension::new(node.clone());
-        assert!(ext.declarations(&ctx_from(&fm)).is_err());
+        let err = ext.declarations(&ctx_from(&fm)).unwrap_err();
+        assert!(
+            err.to_string().contains("https://") || err.to_string().contains("http://"),
+            "expected scheme error, got: {err}"
+        );
+        assert!(err.to_string().contains("runtimes.node.feed-url"), "got: {err}");
     }
 
     #[test]
@@ -218,7 +223,12 @@ mod tests {
         .unwrap();
         let node = fm.runtimes.as_ref().unwrap().node.as_ref().unwrap();
         let ext = NodeExtension::new(node.clone());
-        assert!(ext.declarations(&ctx_from(&fm)).is_err());
+        let err = ext.declarations(&ctx_from(&fm)).unwrap_err();
+        assert!(
+            err.to_string().contains("ADO expression"),
+            "expected injection error, got: {err}"
+        );
+        assert!(err.to_string().contains("runtimes.node.version"), "got: {err}");
     }
 
     /// Default Node install: only a single `Step::Task(UseNode@1)`
diff --git a/src/runtimes/python/extension.rs b/src/runtimes/python/extension.rs
index c55b78f8..08ce008e 100644
--- a/src/runtimes/python/extension.rs
+++ b/src/runtimes/python/extension.rs
@@ -189,7 +189,12 @@ mod tests {
         .unwrap();
         let python = fm.runtimes.as_ref().unwrap().python.as_ref().unwrap();
         let ext = PythonExtension::new(python.clone());
-        assert!(ext.declarations(&ctx_from(&fm)).is_err());
+        let err = ext.declarations(&ctx_from(&fm)).unwrap_err();
+        assert!(
+            err.to_string().contains("https://") || err.to_string().contains("http://"),
+            "expected scheme error, got: {err}"
+        );
+        assert!(err.to_string().contains("runtimes.python.feed-url"), "got: {err}");
     }
 
     #[test]
@@ -200,7 +205,12 @@ mod tests {
         .unwrap();
         let python = fm.runtimes.as_ref().unwrap().python.as_ref().unwrap();
         let ext = PythonExtension::new(python.clone());
-        assert!(ext.declarations(&ctx_from(&fm)).is_err());
+        let err = ext.declarations(&ctx_from(&fm)).unwrap_err();
+        assert!(
+            err.to_string().contains("ADO expression"),
+            "expected injection error, got: {err}"
+        );
+        assert!(err.to_string().contains("runtimes.python.version"), "got: {err}");
     }
 
     /// Locks the `declarations()` override: must return a single