What is the difference between smoke testing and sanity testing?

Smoke testing and sanity testing are both types of software testing techniques used to ensure the stability and basic functionality of an application. However, there are some key differences between the two:

1. Purpose:
- Smoke Testing: The main purpose of smoke testing is to verify if the critical functionalities of the software are working as expected after a new build or release. It is performed to determine if the application is stable enough for further testing.
- Sanity Testing: The primary purpose of sanity testing is to quickly evaluate whether the specific changes or fixes made to the software have not introduced any new issues and the major functionalities are working fine. It is performed to ensure the sanity of the application after minor changes.

2. Scope:
- Smoke Testing: Smoke testing covers a wide range of functionalities and features of the software. It aims to identify major issues or show-stoppers that could prevent further testing.
- Sanity Testing: Sanity testing focuses on specific areas or functionalities of the software that have undergone recent changes. It aims to ensure that the changes have not adversely affected the core functionalities.

3. Execution Time:
- Smoke Testing: Smoke testing is usually performed at the beginning of the testing cycle or after a new build is deployed. It is a quick and shallow test that can be executed within a short period.
- Sanity Testing: Sanity testing is performed after the completion of the smoke testing or when specific changes are made to the software. It is relatively more detailed and time-consuming compared to smoke testing.

4. Depth of Testing:
- Smoke Testing: Smoke testing is a surface-level test that checks the basic functionalities of the software without going into much detail. It does not involve in-depth testing of individual components or modules.
- Sanity Testing: Sanity testing is a more focused test that verifies the specific changes or fixes made to the software. It may involve testing individual components or modules in more detail to ensure their proper functioning.

5. Test Coverage:
- Smoke Testing: Smoke testing aims to cover a broad range of functionalities to identify any major issues or show-stoppers. It does not provide complete test coverage.
- Sanity Testing: Sanity testing focuses on specific areas or functionalities that have undergone changes. It provides relatively higher test coverage for the modified parts of the software.

In summary, smoke testing is performed to ensure the stability of the software after a new build or release, while sanity testing is conducted to quickly evaluate the changes made to the software. Smoke testing has a wider scope and is executed at the beginning of the testing cycle, whereas sanity testing is more focused and performed after smoke testing or specific changes.