Add unit-testing guide.

diff --git a/docs/java/assets/unit-testing/project_difference_with_without_tests_en.png b/docs/java/assets/unit-testing/project_difference_with_without_tests_en.png
new file mode 100644 (file)
index 0000000..7b22e47
Binary files /dev/null and b/docs/java/assets/unit-testing/project_difference_with_without_tests_en.png differ

diff --git a/docs/java/assets/unit-testing/project_difference_with_without_tests_ru.png b/docs/java/assets/unit-testing/project_difference_with_without_tests_ru.png
new file mode 100644 (file)
index 0000000..5c8cd43
Binary files /dev/null and b/docs/java/assets/unit-testing/project_difference_with_without_tests_ru.png differ

diff --git a/docs/java/unit-testing.md b/docs/java/unit-testing.md
new file mode 100644 (file)
index 0000000..d25aac7
--- /dev/null
+++ b/docs/java/unit-testing.md
@@ -0,0 +1,25 @@
+---
+tags:
+    - development
+    - testing
+    - java
+    - unit testing
+---
+
+# Unit Testing
+
+## Unit Testing Goals
+
+It is belived that unit-testing improves quality of the code in your project.
+But this is not the main goal of unit-testing, this is only the positive side-effect.
+The main goal of unit-testing is support the stable growth of software project.
+The key word here is **stable**.
+The following figure displays growth dynamic of typical projects without tests and with tests.
+
+![projects_difference_with_without_tests](./assets/unit-testing/project_difference_with_without_tests_en.png)
+
+Without tests development start fast.
+But as the time goes on, you have to spent more and more time to implement the same functional as at the beginning of the project.
+Develomplent speed reducing is called **software entropy**.
+In the software projects ent
+