xai-org/x-algorithm · error · SemanticCheckFailure

Mock function expects either 1 or 3 arguments but

Error message

Mock function expects either 1 or 3 arguments but %d received

What it means

The Mock(...) testing construct accepts exactly 1 argument (function name) or 3 arguments (name, variable, body). Any other child count is rejected before the mock is registered.

Solutions

1. Use either Mock(fnName) or Mock(fnName, varName, bodyExpr) exactly
2. Remove extra arguments or add the missing variable/body pair

Example fix

// before
Mock("getScore", ToDouble(0.0))
// after
Mock("getScore", "x", ToDouble(0.0))

int n = mockArgCount;
if (n != 1 && n != 3) throw new IllegalArgumentException("Mock needs 1 or 3 args, got " + n);

catch (SemanticCheckFailure e) { if (e.getMessage().contains("Mock function expects")) fixMockShape(); else throw e; }

When it happens

Trigger: `Mock("fn")` (valid), `Mock("fn", "x", expr)` (valid), but `Mock()` or `Mock("fn", expr)` fails with the received count.

Common situations: Writing test mocks by hand with the wrong shape, or copy-pasting between Mock and MockPass forms and miscounting arguments.

Related errors

• MockPass function expects either 1 arguments but
• MockPassAll function expects 1 arguments but
• TestRun function expects 1 arguments but
• The mock for function
• Cannot convert nodes to pairs: offset =

AI-assisted analysis of xai-org/x-algorithm@24c60942c5 (2026-08-28). Data as JSON: /api/errors/c701aa962979b4e2. Report an issue: GitHub.

Appendix: source

Thrown at botmaker/src/java/com/twitter/botmaker/compiler/Compiler.java:1235

        ASTNode bodyNode = createASTNodeTree(context, root.getChild(2));
        context.addMock(funcName, bodyNode);
      } else if (root.getChildCount() == 4) {
        for (int i = 1; i < root.getChildCount() - 1; i++) {
          String funcName = toStringConstant(root.getChild(1));
          String variableName = getVariableName(root.getChild(2));
          Type variableType = Type.listOf(Type.OBJECT);

          CompilerScope scope = context.addScope();
          Parameter parameter = Parameter.open(variableName, variableType);
          scope.defineVariable(parameter);

          ASTNode bodyNode = createASTNodeTree(context, root.getChild(3));
          context.removeScope();

          context.addMock(funcName, variableName, bodyNode);
        }
      } else {
        throw new SemanticCheckFailure(
            String.format("Mock function expects either 1 or 3 arguments but %d received",
                root.getChildCount() - 1)
        );
      }
    } catch (Exception e) {
      throw new SemanticCheckFailure(e);
    }

    return Constant.UNIT;
  }

  private ASTNode toMockPass(
      CompilerContext context,
      String exprText,
      Tree root) throws SemanticCheckFailure {
    try {
      if (root.getChildCount() == 2) {
        String funcName = toStringConstant(root.getChild(1));

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