SDF comes with built-in open-source libraries (learn more about our open source libs). To further increase SDF’s compatibility, it is possible to expand those built-in libs with custom logic. The following guide will explain how to do so, step by step.

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Setup

1

Open an SDF workspace

For the sake of the example, we will use our tests sample workspace. However, you can always use your existing SDF workspace to follow along.To create the tests workspace, run the following command:
sdf new --sample tests && cd tests

run shell
cd tmp && $sdf new --sample tests
There are slight syntax differences for expanding each library. To keep it simple, we will focus our example on tests and point out the implementation differences for other libs.
2

Create a New Libs Folder

Within your workspace, create a new folder. We will call it my_lib, but any name would work. This is where we will add our custom logic in later steps.If you are using the tests example, your workspace should look like this:
run quiet
cd tmp/tests && mkdir my_lib

run shell
cd tmp/tests && tree .
3

Copy SDF's Built-in Lib

One option is to copy the libraries from GitHub:Another option is to copy them from sdfTarget. If you don’t have an sdfTarget directory, all you need to do is to compile your workspace:
sdf compile
If your compilation was successful, you will see sdfTarget in your workspace:
run shell
cd tmp/tests && sdf compile --show none && tree . -L 4 -a
SDF’s libraries will be located under sdfTarget/dbg/.lib.Let’s copy sdf_test to our new custom libraries folder:
run quiet
cd tmp/tests && cp -R sdfTarget/dbg/.lib/sdf_test my_lib

run error
cd tmp/tests && tree ./my_lib
You can choose to keep the library name as is, sdf_test, or change it if there’s another name you’d prefer to use.
4

Add Custom Library to the Workspace YML

Now, we need to add our new library to the workspace configuration. In our workspace.sdf.yml file, let’s add the following section:
workspace:
    ...
    dependencies:
        - name: sdf_test
          path: my_lib/sdf_tests  <-- or a different folder name
    ...
Notice, we are using SDF’s built-in library name, sdf_test. However, we can also choose a different name to our library. If we decide to do so, we’ll need to indicate it in the defaults.Let’s assume we call the new tests library new_tests:
workspace:
    ...
    dependencies:
        - name: new_tests  <-- this is the new lib name
          path: my_lib/sdf_tests  <-- or a different folder name
    defaults:
        test-lib: new_tests  <-- this is the new lib name
    ...
If we want to add another type of custom lib with a non-default name, we should add to the defaults section:
...
defaults:
    materialization-lib: new_mat  <-- This is a non-default name
...
  • We can have more than one custom lib added to a workspace. Each lib is independent of the rest.
  • We can create an environment to include the custom libs rather than include it in the main workspace configuration. It’ll look like this:
workspace:
    ...
---
environment:
    name: custom_libs
    dependencies:
        - name: sdf_test
          path: my_lib/sdf_test
    ...
5

Expand Your Lib

Let’s add some custom logic!Open the lib file. It will be located under my_lib/sdf_test/macro/test.jinja. If you changed any folder names, make sure to apply the changes to locate the relevant file.Copy the following macro to the top of your custom tests lib:
my_lib/sdf_test/macro/test.jinja
{% macro custom_column_test(severity, column_name) -%}
    COUNT(CASE WHEN {{ column_name }} > 1000 THEN 1 ELSE NULL END) > 0 
    ==> 
    '{{severity}}: column {{ column_name }} is over 1000"' 
{%- endmacro %}
We are keeping it simple and merely checking that the column value is below 1000, but of course, you can implement any custom and complex logic here.
6

Try It!

First, we need to add the test to our table yml file, just like for SDF’s built-in tests (to learn more, visit our Tests Guide). In the file src_metadata/raw_inapp_events.sdf.yml, add our new custom test to the column event_name:
src_metadata/raw_inapp_events.sdf.yml
table:
    ...
    columns:
        - name: index
            description: row_number
            tests:
                - expect: custom_column_test()  <-- this is our new test!
                  severity: warning
    ...
Let’s run the test! In your terminal, execute:
sdf test
The test passed!
add yml
custom_libs/raw_inapp_events.sdf.yml -> tests/src_metadata/raw_inapp_events.sdf.yml

add yml
custom_libs/workspace.sdf.yml -> tests/workspace.sdf.yml

add jinja
custom_libs/test.jinja -> tests/my_lib/sdf_test/macros/test.jinja

run shell
cd tmp/tests && sdf test
We can look at the compiled tests query located in the file sdftarget/dbg/preprocessed/tests_workspace/pub/test_raw_inapp_events.sql. Notice our custom logic in the compiled query:
run shell
cd tmp/tests && cat sdftarget/dbg/preprocessed/tests_workspace/pub/test_raw_inapp_events.sql