Gray Box Testing

[ test design ]

In gray box testing we have some knowledge about the internal structure of the application, but, as in black box testing, we mostly rely on the specification.

For example, we might have access to the database schema and spot bugs already at the documentation review stage. We will cover databases later here.

Analyzing Database-Level Constraints

Access to the database schema allows the tester to check in advance whether the requirements match the actual table structure.

Below are examples of bugs that can be found simply by comparing the requirements with the schema.

Data type

Requirements	Database
The field may contain any characters	The field has a numeric type `INTEGER`
The field must store text up to 200 characters long	The field is limited to 100 characters `VARCHAR(100)`

Bug: A smaller size constraint in the database may lead to errors when writing or updating data.

Integrity constraint

Requirements	Database
The field may be empty	The field has a constraint `NOT NULL`

Bug: NOT NULL constraint may cause an error when inserting a record with an empty value.

Value uniqueness

Requirements	Database
Values in the field are not unique	The field has a constraint `UNIQUE`

Bug: UNIQUE constraint may cause an error when inserting a record with a duplicate value.

Task

Review the API requirements and the database schema. Perform gray box testing. When the server receives a request, it updates the name column of the table cat.

HTTP request form

Endpoint

HTTP method

Select header value Content-Type

Request body

Server response

Requirements for the API:

Endpoint /hello-gray-box-server
HTTP method that corresponds to updating data on the server
Header with a content type application/json
(indicates that data will be sent in JSON format)
Request body must contain the key name with any string value in JSON format

Key	Type	Required	Constraints
name	string	+	1 to 30 characters

Cat table schema:

Field	Type	Description
id	`integer`	Record identifier
name	`varchar(16)`	Name
age	`integer`	Age

Field constraints:

varchar(16) - string up to 16 characters
integer - number

We did something similar in the task from the API. This time, our goal is to find a bug using both the requirements and additional knowledge of the database schema.