Revert testing-guide.md

Author: Vitalii-code

Sprint-3/1-implement-and-rewrite-tests/testing-guide.md

@@ -7,11 +7,10 @@ Input  ──▶  Function  ──▶  Output
 ```
 
 A function
-
 - Takes **input** (via **arguments**)
 - Does some work
 - Produces **one output** (via a **return value**)
-
+ 
 Example:
 
 ```
@@ -20,18 +19,17 @@ sum(2, 3) → 5
 
 Important idea: the same input should produce the same output.
 
-## 2. Testing Means Predicting
 
-Testing means:
+## 2. Testing Means Predicting
 
+Testing means: 
 > If I give this input, what output should I get?
 
+
 ## 3. Choosing Good Test Values
 
 ### Step 1: Determining the space of possible inputs
-
 Ask:
-
 - What type of value is expected?
 - What values make sense?
   - If they are numbers:
@@ -41,7 +39,7 @@ Ask:
     - What are their length and patterns?
 - What values would not make sense?
 
-### Step 2: Choosing Good Test Values
+### Step 2: Choosing Good Test Values 
 
 #### Normal Cases
 
@@ -50,9 +48,10 @@ These confirm that the function works in normal use.
 - What does a typical, ordinary input look like?
 - Are there multiple ordinary groups of inputs? e.g. for an age checking function, maybe there are "adults" and "children" as expected ordinary groups of inputs.
 
+  
 #### Boundary Cases
 
-Test values exactly at, just inside, and just outside defined ranges.
+Test values exactly at, just inside, and just outside defined ranges. 
 These values are where logic breaks most often.
 
 #### Consider All Outcomes
@@ -65,7 +64,6 @@ Every outcome must be reached by at least one test.
 #### Crossing the Edges and Invalid Values
 
 This tests how the function behaves when assumptions are violated.
-
 - What happens when input is outside of the expected range?
 - What happens when input is not of the expected type?
 - What happens when input is not in the expected format?
@@ -75,19 +73,18 @@ This tests how the function behaves when assumptions are violated.
 ### 1. Using `console.assert()`
 
 ```javascript
-// Report a failure only when the first argument is false
-console.assert(sum(4, 6) === 10, "Expected 4 + 6 to equal 10");
+  // Report a failure only when the first argument is false
+  console.assert( sum(4, 6) === 10, "Expected 4 + 6 to equal 10" );
 ```
 
 It is simpler than using `if-else` and requires no setup.
-
+  
 ### 2. Jest Testing Framework
 
 ```javascript
-  describe("Description for this case used for grouping")
   test("Should correctly return the sum of two positive numbers", () => {
     expect( sum(4, 6) ).toEqual(10);
-    ... // Can test multiple samples
+    ... // Can test multiple samples 
   });
 
 ```