Vim test_ API to port to Neovim

vim_test_api_to_port.txt

test_null_channel()					*test_null_channel()*
		Return a |Channel| that is null. Only useful for testing.
		{only available when compiled with the +channel feature}

		Return type: |Channel|

test_null_function()					*test_null_function()*
		Return a |Funcref| that is null. Only useful for testing.

		Return type: func(...): unknown

test_null_job()						*test_null_job()*
		Return a |Job| that is null. Only useful for testing.
		{only available when compiled with the +job feature}

		Return type: |job|

test_null_partial()					*test_null_partial()*
		Return a |Partial| that is null. Only useful for testing.

		Return type: func(...): unknown

test_null_tuple()					*test_null_tuple()*
		Return a |Tuple| that is null. Only useful for testing.

		Return type: |Tuple|

test_refcount({expr})					*test_refcount()*
		Return the reference count of {expr}.  When {expr} is of a
		type that does not have a reference count, returns -1.  Only
		to be used for testing.

		Can also be used as a |method|: >
			GetVarname()->test_refcount()
<
		Return type: |Number|

test_unknown()						*test_unknown()*
		Return a value with unknown type. Only useful for testing.

		Return type: unknown

test_void()						*test_void()*
		Return a value with void type. Only useful for testing.

		Return type: void


VV(VV__NULL_STRING,     "_null_string",     VAR_STRING, VV_RO),
VV(VV__NULL_LIST,       "_null_list",       VAR_LIST, VV_RO),
VV(VV__NULL_DICT,       "_null_dict",       VAR_DICT, VV_RO),
VV(VV__NULL_BLOB,       "_null_blob",       VAR_BLOB, VV_RO),

/// Vimscript variable types, for use in typval_T.v_type
typedef enum {
  VAR_UNKNOWN = 0,  ///< Unknown (unspecified) value.
  VAR_NUMBER,       ///< Number, .v_number is used.
  VAR_STRING,       ///< String, .v_string is used.
  VAR_FUNC,         ///< Function reference, .v_string is used as function name.
  VAR_LIST,         ///< List, .v_list is used.
  VAR_DICT,         ///< Dict, .v_dict is used.
  VAR_FLOAT,        ///< Floating-point value, .v_float is used.
  VAR_BOOL,         ///< true, false
  VAR_SPECIAL,      ///< Special value (null), .v_special is used.
  VAR_PARTIAL,      ///< Partial, .v_partial is used.
  VAR_BLOB,         ///< Blob, .v_blob is used.
} VarType;