code: def test_simple_c_codegen():
      x, y, z = symbols("x,y,z")
      expr = (x + y) * z
      expected = [
          (
              "file.c",
              '#include "file.h"\n'
              "#include <math.h>\n"
              "double test(double x, double y, double z) {\n"
              "   double test_result;\n"
              "   test_result = z*(x + y);\n"
              "   return test_result;\n"
              "}\n",
          ),
          (
              "file.h",
              "#ifndef PROJECT__FILE__H\n"
              "#define PROJECT__FILE__H\n"
              "double test(double x, double y, double z);\n"
              "#endif\n",
          ),
      ]
      result = codegen(
          ("test", expr), "C", "file", header=False, empty=False
      )
      assert result == expected
  
imports: from io import StringIO
  from sympy.core import symbols, Eq, pi, Catalan, Lambda, Dummy
  from sympy.core.relational import Equality
  from sympy.core.symbol import Symbol
  from sympy.functions.special.error_functions import erf
  from sympy.integrals.integrals import Integral
  from sympy.matrices import Matrix, MatrixSymbol
  from sympy.utilities.codegen import codegen, make_routine, CCodeGen, C89CodeGen, C99CodeGen, InputArgument, CodeGenError, FCodeGen, CodeGenArgumentListError, OutputArgument, InOutArgument
  from sympy.testing.pytest import raises
  from sympy.utilities.lambdify import implemented_function
label_desc: Use image node_id 11 for calling a global function with example usage: test_simple_c_codegen() without return types