August 17, 2023

tAssert – Docs for ESB 5.x



tAssert Properties

The tAssert component works alongside tAssertCatcher to evaluate the status of a Job execution. It
concludes with the boolean result based on an assertive statement related to the
execution and feed the result to tAssertCatcher for
proper Job status presentation.

Component family

Logs & Errors



Provides the Job status messages to tAssertCatcher.


Generates the boolean evaluation on the concern for the Job
execution status. The status includes:

Ok: the Job execution

Fail: the Job execution fails.
The tested Job’s result does not match the expectation or an
execution error occured at runtime.

Basic settings


Type in your descriptive message to help identify the assertion of
a tAssert.



Type in the assertive statement you base the evaluation on.

Global Variables

ERROR_MESSAGE: the error message generated by the
component when an error occurs. This is an After variable and it returns a string. This
variable functions only if the Die on error check box is
cleared, if the component has this check box.

A Flow variable functions during the execution of a component while an After variable
functions after the execution of the component.

To fill up a field or expression with a variable, press Ctrl +
to access the variable list and choose the variable to use from it.

For further information about variables, see Talend Studio
User Guide.


This component follows the action the assertive condition is
directly related to. It can be the intermediate or end component of
the main Job, or the start, intermediate or end component of the
secondary Job.


The evaluation of tAssert is
captured only by tAssertCatcher.

Scenario 1: Viewing product orders status (on a daily basis) against a benchmark

This scenario allows you to insert the orders information into a database table and to
evaluate the orders status (every day once scheduled to run) by using tAssert to compare the orders against a fixed number and
tAssertCatcher to indicate the results. In this
case, Ok is returned if the number of orders is greater
than 20 and Failed is returned if the number of orders
is less than 20.

In practice, this Job can be scheduled to run every day for the daily orders report
and tFixedFlowInput as well as tLogRow are replaced by input and output components in the Database/File

Linking the components

  1. Drop tFixedFlowInput, tMysqlOutput, tAssert, tAssertCatcher,
    and tLogRow onto the workspace.

  2. Rename tFixedFlowInput as orders, tAssert
    as orders >=20, tAssertCatcher as catch comparison
    and tLogRow as
    ok or failed.

  3. Link tFixedFlowInput to tMysqlOutput using a Row > Main

  4. Link tFixedFlowInput to tAssert using the Trigger > On Subjob OK

  5. Link tAssertCatcher to tLogRow using a Row > Main


Configuring the components

  1. Double-click tFixedFlowInput to open its
    Basic settings view.


    Select Use Inline Content (delimited
    in the Mode

    In the Content field, enter the data to
    write to the Mysql database, for example:

    Note that the orders listed are just for illustration of how tAssert functions and the number here is less
    than 20.

  2. Click the Edit schema button to open the
    schema editor.

  3. Click the [+] button to add four columns,
    namely product_id, product_name, date and price, of the
    String, Date, Float types

    Click OK to validate the setup and close
    the editor.

  4. Double-click tMysqlOutput to display the
    Basic settings view.

  5. In the Host, Port, Database, Username and Password fields, enter the connection details and the
    authentication credentials.

  6. In the Table field, enter the name of the
    table, for example order.

  7. In the Action on table list, select the
    option Drop table if exists and

  8. In the Action on data list, select the
    option Insert.

  9. Double-click tAssert to display the
    Basic settings view.

  10. In the description field, enter the
    descriptive information for the purpose of tAssert in this case.

  11. In the expression field, enter the
    expression allowing you to compare the data to a fixed number:

  12. Double-click tLogRow to display the
    Basic settings view.

  13. In the Mode area, select Table (print values in cells of a table) for a
    better display.

Executing the Job

  1. Press Ctrl + S to save the Job.

  2. Press F6 to run the Job.


    As shown above, the orders status indicates Failed as the number of orders is less than 20.

Scenario 2: Setting up the assertive condition for a Job execution

This scenario describes how to set up an assertive condition in tAssert in order to evaluate that a Job execution succeeds or not.
Moreover, you can also find out how the two different evaluation results display and the
way to read them. Apart from tAssert, the scenario uses
the following components as well:

  • tFileInputDelimited and tFileOutputDelimited. The two components compose the main Job of
    which the execution status is evaluated. For the detailed information on the two
    components, see tFileInputDelimited and tFileOutputDelimited.

  • tFileCompare. It realizes the comparison
    between the output file of the main Job and a standard reference file. The
    comparative result is evaluated by tAssert
    against the assertive condition set up in its settings. For more detailed
    information on tFileCompare, see tFileCompare.

  • tAssertCatcher. It captures the evaluation
    generated by tAssert. For more information on
    tAssertCatcher, see tAssertCatcher.

  • tLogRow. It allows you to read the captured
    evaluation. For more information on tLogRow,
    see tLogRow.

First proceed as follows to design the main Job:

  • Prepare a delimited .csv file as the source file read by
    your main Job.

  • Edit two rows in the delimited file. The contents you edit are not important,
    so feel free to simplify them.

  • Name it source.csv.

  • In Talend Studio, create a new job

  • Place tFileInputDelimited and tFileOutputDelimited on the workspace.

  • Connect them with a Row Main link to create
    the main Job.

  • Double-click tFileInputDelimited to open its
    Component view.

  • In the File Name field of the Component view, fill in the path or browse to

  • Still in the Component view, set Property Type to Built-In and click schema_icon.png next to Edit schema to
    define the data to pass on to tFileOutputDelimited. In the scenario, define the data presented
    in source.csv you created.

For more information about schema types, see Talend Studio User Guide.

  • Define the other parameters in the corresponding fields according to
    source.csv you created.

  • Double-click tFileOutputDelimited to open its
    Component view.

  • In the File Name field of the Component view, fill in or browse to specify the path
    to the output file, leaving the other fields as they are by default.

  • Press F6 to execute the main Job. It reads
    source.csv, pass the data to
    and output an delimited file,

Then contine to edit the Job to see how tAssert
evaluates the execution status of the main Job.

  • Rename out.csv as reference.csv.This
    file is used as the expected result the main Job should output.

  • Place tFileCompare, tAssert and tLogRow on the

  • Connect them with Row Main link.

  • Connect tFileInputDelimited to tFileCompare with OnSubjobOk link.

  • Double-click tFileCompare to open its
    Component view.

  • In the Component view, fill in the
    corresponding file paths in the File to compare
    field and the Reference file field, leaving the
    other fields as default.


For more information on the tFileCompare component,
see tFileCompare.

  • Then click tAssert and click the Component tab on the lower side of the

  • In the Component view, edit the assertion
    row2.differ==0 in the expression field and the descriptive message of the assertion in
    description field.

In the expression field, row2 is the
data flow transmissing from tFileCompare to tAssert, differ is one of the columns of the
tFileCompare schema and presents whether the
compared files are identical, and 0 means no difference is detected between
the out.csv and reference.csv by tFileCompare. Hence when the compared files are identical,
the assertive condition is thus fulfilled, tAssert
concludes that the main Job succeeds; otherwise, it concludes failure.


The differ column is in the read-only tFileCompare schema. For more information on its schema, see tFileCompare.

  • Press F6 to execute the Job.

  • Check the result presented in the Run


The console shows the comparison result of tFileCompare: Files are identical. But you find nowhere the
evaluation result of tAssert.

So you need tAssertCatcher to capture the

  • Place tAssertCatcher and tLogRow on the workspace.

  • Connect them with Row Main link.

  • Use the default configuration in the Component view of tAssertCatcher.

  • Press F6 to execute the Job.

  • Check the result presented in the Run view.
    You will see the Job status information is added in:



The descriptive information on JobAssertion in the console is
organized according to the tAssertCatcher schema. This
schema includes, in the following order, the execution time, the process ID, the project
name, the Job name, the code language, the evaluation origin, the evaluation result,
detailed information of the evaluation, descriptive message of the assertion. For more
information on the schema of tAssertCatcher, see tAssertCatcher.

The console indicates that the execution status of Job
JobAssertion is Ok. In addition to the
evalution, you can still see other descriptive information about
JobAssertion including the descriptive message you have edited
in the Basic settings of tAssert.

Then you will perform operations to make the main Job fail to generate the expected
file. To do so, proceed as follows in the same Job you have executed:

  • Delete a row in reference.csv.

  • Press F6 to execute the Job again.

  • Check the result presented in Run



The console shows that the execution status of the main Job is
Failed. The detailed explanation for this status is closely
behind it, reading Test logically failed.

You can thus get a basic idea about your present Job status: it fails to generate the
expected file because of a logical failure. This logical failure could come from a
logical mistake during the Job design.

The status and its explanatory information are presented respectively in the
status and the substatus columns of the
tAssertCatcher schema. For more information on the
columns, see tAssertCatcher.

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