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When looking and Behavior-Driven development, "Behavior-driven development is an extension of test-driven development" (From Wikipedia). Researching around various articles, behavior-driven development is a form of TDD which is writing unit tests. At the same time, BDD focuses on business value, but not all modules provide direct business value on their own. (This is often true in embedded software development.) Business value is only added when separate modules are used together. So it seems contradictory that behavior tests focused on business requirements can be implemented using unit tests testing individual modules.

Does behavior driven development work on the level of writing individual unit tests for a single unit. Or is it actually more closely related to integration testing, crossing over multiple units?

Put in an a example: How do you write behavior driven "unit tests" for low-level modules such as a memory access module or a component driver if that low-level component doesn't provide any business value on its own?

Then, in the other direction, how do you write behavior driven "unit tests" for a single high-level component if the business requirement can only be validated when integrating low-level modules and can't be validated using mocks of the low-level module?

Related, but doesn't answer how to test the low-level modules which don't have requirements: How to use unit tests when using BDD?

When looking and Behavior-Driven development, "Behavior-driven development is an extension of test-driven development" (From Wikipedia). Researching around various articles, behavior-driven development is a form of TDD which is writing unit tests. At the same time, BDD focuses on business value, but not all modules provide direct business value on their own. (This is often true in embedded software development.) Business value is only added when separate modules are used together. So it seems contradictory that behavior tests focused on business requirements can be implemented using unit tests testing individual modules.

Does behavior driven development work on the level of writing individual unit tests for a single unit. Or is it actually more closely related to integration testing, crossing over multiple units?

Put in an a example: How do you write behavior driven "unit tests" for low-level modules such as a memory access module or a component driver if that low-level component doesn't provide any business value on its own?

Then, in the other direction, how do you write behavior driven "unit tests" for a single high-level component if the business requirement can only be validated when integrating low-level modules and can't be validated using mocks of the low-level module?

Related Question, but doesn't fully distinguish BDD from TDD: How to use unit tests when using BDD?

When looking and Behavior-Driven development, "Behavior-driven development is an extension of test-driven development" (From Wikipedia). Researching around various articles, behavior-driven development is a form of TDD which is writing unit tests. At the same time, BDD focuses on business value, but not all modules provide direct business value on their own. (This is often true in embedded software development.) Business value is only added when separate modules are used together. So it seems contradictory that behavior tests focused on business requirements can be implemented using unit tests testing individual modules.

Does behavior driven development work on the level of writing individual unit tests for a single unit. Or is it actually more closely related to integration testing, crossing over multiple units?

Put in an a example: How do you write behavior driven "unit tests" for low-level modules such as a memory access module or a component driver if that low-level component doesn't provide any business value on its own?

Then, in the other direction, how do you write behavior driven "unit tests" for a single high-level component if the business requirement can only be validated when integrating low-level modules and can't be validated using mocks of the low-level component?

When looking and Behavior-Driven development, "Behavior-driven development is an extension of test-driven development" (From Wikipedia). Researching around various articles, behavior-driven development is a form of TDD which is writing unit tests. At the same time, BDD focuses on business value, but not all modules provide direct business value on their own. (This is often true in embedded software development.) Business value is only added when separate modules are used together. So it seems contradictory that behavior tests focused on business requirements can be implemented using unit tests testing individual modules.

Does behavior driven development work on the level of writing individual unit tests for a single unit. Or is it actually more closely related to integration testing, crossing over multiple units?

Put in an a example: How do you write behavior driven "unit tests" for low-level modules such as a memory access module or a component driver if that low-level component doesn't provide any business value on its own?

Then, in the other direction, how do you write behavior driven "unit tests" for a single high-level component if the business requirement can only be validated when integrating low-level modules and can't be validated using mocks of the low-level module?

Related, but doesn't answer how to test the low-level modules which don't have requirements: How to use unit tests when using BDD?