test(mir-builder): add test for imports resolution

Add test_imports_resolution to verify MatI64 imports work correctly

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/host_providers/mir_builder.rs

@@ -71,3 +71,64 @@ pub fn program_json_to_mir_json_with_imports(program_json: &str, imports: HashMa
         }
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_imports_resolution() {
+        // Program JSON with MatI64.new(4, 4)
+        let program_json = r#"{
+            "version": 0,
+            "kind": "Program",
+            "body": [
+                {
+                    "type": "Local",
+                    "name": "n",
+                    "expr": {"type": "Int", "value": 4}
+                },
+                {
+                    "type": "Local",
+                    "name": "A",
+                    "expr": {
+                        "type": "Method",
+                        "recv": {"type": "Var", "name": "MatI64"},
+                        "method": "new",
+                        "args": [
+                            {"type": "Var", "name": "n"},
+                            {"type": "Var", "name": "n"}
+                        ]
+                    }
+                },
+                {
+                    "type": "Return",
+                    "expr": {
+                        "type": "Method",
+                        "recv": {"type": "Var", "name": "A"},
+                        "method": "at",
+                        "args": [
+                            {"type": "Int", "value": 0},
+                            {"type": "Int", "value": 0}
+                        ]
+                    }
+                }
+            ]
+        }"#;
+
+        // Create imports map
+        let mut imports = HashMap::new();
+        imports.insert("MatI64".to_string(), "MatI64".to_string());
+
+        // Call with imports
+        let result = program_json_to_mir_json_with_imports(program_json, imports);
+
+        // Should succeed
+        assert!(result.is_ok(), "Failed with error: {:?}", result.err());
+
+        let mir_json = result.unwrap();
+        // MIR JSON should contain functions
+        assert!(mir_json.contains("functions"), "MIR JSON should contain functions");
+        eprintln!("[test] MIR JSON generated successfully with MatI64 imports");
+    }
+}