Created faking and mocking functions #346

v-maliutin · 2025-03-13T17:18:42Z

I developed some functions to make writing tests easier. There are examples in the source code. Also, I wrote an article on habr. Here it is https://habr.com/ru/companies/gnivc/articles/877314/. I know it is in Russian, but hope modern translation will help.
Anyway such functionality is in any modern language and wide known. I just bringing it in PG world.
One more thing. I am going to introduce my work and pgTap at pgConf in Moscow on March 31 2025.

mock and fake functions

…in/pgtap into fake_and_mock_functions just pulling from github

…cements to other routines

Fake and mock functions

v-maliutin · 2025-05-13T10:59:32Z

@theory Hi! Could you please let me know what you think about my PR. I'd appreciate it.

theory · 2025-05-22T20:46:09Z

Sorry, @v-maliutin, hyper busy rn, but will get to it.

jnasbyupgrade · 2025-06-02T23:46:20Z

Not a full review, but a couple comments:

AFAIK, there's no reason to modify the unpackaged script.

Instead of building a function body via ||, I think it would be a lot clearer to use format().

… convenient way to debug.

v-maliutin · 2025-08-24T15:00:05Z

Not a full review, but a couple comments:

AFAIK, there's no reason to modify the unpackaged script.

Instead of building a function body via ||, I think it would be a lot clearer to use format().

@jnasbyupgrade thank you for your review. Rolled back changes in Unpackaged
Regarding format vs ||. May I stay as is? Just I always lost in '%1L, %2I, %3s'. Especially when there are a lot of %. Anyway I can fix it if you insist. This is not a big problem for me.

theory

Looks super interesting, though I'm not sure they need to be procedures. I requested some change, but the big thing that's missing here is documentation. It would be super helpful for comments in the code to explain what each bit is doing and why (primary example, when it creates two mock functions without explanation). But also the new features should be documented in doc/pgtap.mmd, perhaps with a tutorial.

sql/pgtap.sql.in

v-maliutin · 2025-11-01T03:58:04Z

@theory

Hi, I am going to implement the following features. Please let me know if you think they are a good idea too.

Spy on a routine. This feature would log parameter values.

Spy on a table. A trigger logging inserted/updated/deleted values. Something like a profiler.

Make the output of runtests a standard dataset. It would help to write a tool running tests. Let's say a plugin to DBeaver.

Mocking of procedures.

Special mock to arrange a profiler feature

theory

Honestly this is a huge feature that I think should probably be its own extension, either distributed separately and depending on pgtap (perhaps a release that includes changes to tap_funky that it requires) or else a separate extension as part of the pgTAP distribution. I'm leaning toward the former, at least as you work through the process, because I'm not sure I have the capacity to take on maintaining such a huge feature I don't use. I'm happy to review code and make recommendations if you decide to distribute it as its own extension.

theory · 2025-11-01T15:51:19Z

doc/pgtap.mmd

+Mocking, faking and making your test independent
+================================================
+
+Examples of implementing mocking and faking functionality can be found in my fork [`on GitHub`](https://github.com/v-maliutin/pgtap/tree/examples_forking_and_mocking/examples).


For permanent documentation I wouldn't refer to "my fork", just link to the source.

theory · 2025-11-01T15:52:20Z

doc/pgtap.mmd

+
+Let's say we have a main table and a subordinate table.
+
+    CREATE TABLE master(


Let's avoid the term "master"; how about "parent"?

theory · 2025-11-01T15:53:56Z

doc/pgtap.mmd

+
+### `fake_table()` ###
+
+    PERFORM fake_table( :_table_ident, :_make_table_empty, :_leave_primary_key, :_drop_not_null, :_drop_collation, :_drop_partitions );


None of the existing doc params have underscores; please remove them.

theory · 2025-11-01T15:54:49Z

doc/pgtap.mmd

+**Parameters**
+
+`:_table_ident`
+: Text array of tables to be faked in the format 'my_schema.my_table'. Required.


Why does this param support multiple tables but the rest refer to a single table?

theory · 2025-11-01T15:55:42Z

doc/pgtap.mmd

+        _drop_collation => false
+    );
+
+ One note. The parameters _leave_primary_key and _drop_not_null are currently contradictory.


Use backticks for parameter names.

theory · 2025-11-01T16:01:41Z

sql/pgtap.sql.in

+    _func_schema text
+    , _func_name text
+    , _func_args text
+    , _return_set_value text default null
+    , _return_scalar_value anyelement default null::text


Remove leading underscores.

theory · 2025-11-01T16:04:43Z

sql/pgtap.sql.in

+	            return query execute _query(_name);
+			end;
+	        %4$sfunction%4$s;',
+			_func_schema/*1*/, _func_name/*2*/, _func_result_type/*3*/, '$'/*4*/);


So it replaces the function in the same schema? I presume you're depending on a transaction ROLLBACK to rollback the mock function, yes?

theory · 2025-11-01T16:09:24Z

sql/pgtap.sql.in

+			_func_schema/*1*/,  _func_name/*2*/, _func_args/*3*/, _func_result_type/*4*/,
+			_func_language/*5*/, _return_scalar_value/*6*/, pg_typeof(_return_scalar_value)/*7*/, '$'/*8*/);
+	    execute _mock_ddl;
+	end if;


Seems like there are some conditions that are ignored here, yes? Should it raise an error for unsupported conditions, e.g., a set-returning C function.

theory · 2025-11-01T16:13:45Z

sql/pgtap.sql.in

+    _json text;
+    _columns text;
+--returns a query which you can execute and see your table as normal dataset
+--you can find the returned query in the output window in DBeaver, where we see raise notice command output


I don't understand what Beaver has to do with this. I have never used it, and it shouldn't be a requirement for users to have it.

theory · 2025-11-01T16:15:51Z

test/sql/faketable.sql

+
+CREATE FUNCTION test_faking_functionality() RETURNS SETOF TEXT AS $$
+BEGIN
+	perform fake_table(


The use of procedures will either require that this functionality not be part of pgTAP or that there be patches to remove it for Postgres versions that don't support it.

theory · 2025-11-01T16:22:15Z

@theory

Hi, I am going to implement the following features. Please let me know if you think they are a good idea too.

Seems like it, yes, but again I think this is full-featured enough that it might be better developed and distributed as its own extension.

malyutinvn and others added 13 commits December 31, 2024 07:26

mock and fake functions

5179a88

Add files via upload

463c367

mock and fake functions

there are several functions to fake a table and mock a function

4c29b12

Merge branch 'fake_and_mock_functions' of https://github.com/v-maliut…

65d0f50

…in/pgtap into fake_and_mock_functions just pulling from github

added example how to use mock and fake functions

9ab57ca

mock_func is able to mock plpgsql and sql functionality, + some enhan…

69aa765

…cements to other routines

fixed tap_funky and implemented call_count

0f8c32d

fixed returns column in tap_funky and added a regression test

c733367

wrote self-tests on faking functionality

401bcc2

Prettying up examples

c958455

Leave a single version

19c700a

Merge pull request #1 from v-maliutin/fake_and_mock_functions

2231bec

Fake and mock functions

Merge branch 'main' into main

3f8d7eb

mslava added 5 commits August 24, 2025 20:56

Created a new function to print a query instead of a table. Just more…

8dce627

… convenient way to debug.

No modifications in unpackaged

80fdb8a

Merge remote-tracking branch 'origin/main'

1604a83

No modifications in unpackaged

6226807

Merge branch 'fake_and_mock_functions'

e660e9d

theory requested changes Sep 6, 2025

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mslava added 7 commits September 23, 2025 12:59

Function instead of procedures + format function instead of ||

f57c7e0

Documentation on fake_table function

a2af1dd

Documentation on mock_func function

6de5e8a

Updated pgtap.sql.in

edf0f9a

Add ability to mock a view + some fixes

2273ba2

Fixes, new tests, new documentation

4ae191b

fixed a couple of typos

5baf8c7

v-maliutin requested a review from theory October 25, 2025 11:49

theory reviewed Nov 1, 2025

View reviewed changes


		Let's say we have a main table and a subordinate table.

		CREATE TABLE master(


		### `fake_table()` ###

		PERFORM fake_table( :_table_ident, :_make_table_empty, :_leave_primary_key, :_drop_not_null, :_drop_collation, :_drop_partitions );

Created faking and mocking functions #346

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Created faking and mocking functions #346

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v-maliutin commented Mar 13, 2025

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v-maliutin commented Nov 1, 2025

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theory commented Nov 1, 2025

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