Add ADR 0003 - Switch Test Assertions from Truth to AssertK

docs/architecture/adr/0003-switch-test-assertions-from-truth-to-assertk.md

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+# Switch Test Assertions from Truth to assertk
+
+## Status
+
+- **Accepted**
+
+## Context
+
+Our project has been using the Truth testing library for writing tests. While Truth has served us well, it is primarily
+designed for Java and lacks some features that make our Kotlin tests more idiomatic and expressive. As our codebase is
+[primarily Kotlin](0001-switch-from-java-to-kotlin.md), we have been looking for a testing library that is more aligned
+with Kotlin's features and idioms.
+
+## Decision
+
+We have decided to use [assertk](https://github.com/willowtreeapps/assertk) as the default assertions framework for
+writing tests in our project. assertk provides a fluent API that is very similar to Truth, making the transition easier.
+Moreover, it is designed to work well with Kotlin, enabling us to leverage Kotlin-specific features in our tests.
+
+We've further committed to converting all pre-existing tests from Truth to assertk.
+
+## Consequences
+
+**Note**: The migration of all Truth tests to assertk has already been completed.
+
+- **Positive Consequences**
+
+  - **Ease of Transition**: The syntax of assertk is very similar to Truth, which makes the migration process smoother.
+  - **Kotlin-Friendly**: assertk is designed specifically for Kotlin, allowing us to write more idiomatic and
+    expressive Kotlin tests.
+
+- **Negative Consequences**
+
+  - **Dependency**: While we are replacing one library with another, introducing a new library always carries the risk
+    of bugs or future deprecation.
+  - **Migration Effort**: Existing tests written using Truth will need to be migrated to use assertk, requiring some
+    effort, although mitigated by the similar syntax.