docs(tests): add test cases for absolute start dates and bar trimming on time filter change

Author: DavidRajnoha

docs/incident_detection/tests/2.ui_display_flows.md

@@ -109,6 +109,26 @@ start,end,alertname,namespace,severity,silenced,labels
   - Check the "last updated date" field
   - Verify that the format changes without the need to reload the page
 
+### 2.3.2 Incident Bar Trimming on Time Filter Change
+**BUG**: When "Last N Days" is shorter than an incident's duration, the bar should be visually trimmed to show only the portion within the selected time window.  
+**Automation Status**: NOT AUTOMATED
+
+**Background**:
+- Incorrect behavior: Changing time filter "squashes" the X-axis to the right while still showing the full incident bar
+- Correct behavior: Incident bar is trimmed/clipped to only display the portion that falls within the selected time range
+
+- [ ] **Bar Trimming - Long Incident with Short Filter**: Create an incident spanning 15 days
+  - With "Last 15 days": Full incident bar visible with correct proportional width
+  - Set time filter to "Last 7 days"
+  - Verify the incident bar is trimmed to show only the 7-day portion (not the full 15-day bar)
+  - Verify the X-axis scale matches the 7-day window (not squashed to the right)
+  - Verify the bar starts at the left edge of the chart (since incident started before the 7-day window)
+
+- [ ] **Tooltip Accuracy After Trimming**: Hover over a trimmed incident bar
+  - Verify tooltip shows the actual absolute Start date (which may be before the visible window)
+  - Verify tooltip shows correct End date
+  - Verify the displayed duration reflects the full incident, not just the visible portion
+
 ### 2.4 Silences labels (Not Automated)
 - Verify that information about silences is contained in the alert name 
   as `NetworkLatencyHigh (silenced)` instead of the additional `silenced=true`

docs/incident_detection/tests/3.api_calls_data_loading_flows.md

@@ -84,8 +84,27 @@ start,end,alertname,namespace,severity,silenced,labels
   - Verify the latest query end time param is within the last 5 minutes
 
 
-  ### 3.4 Data Integrity
-  **NEW, NOT AUTOMATED, TODO COO 1.4**
+### 3.4 15-Day Data Loading with "Last N Days" Filtering
+**FEATURE**: UI always loads 15 days of data (one query_range call per day), then filters client-side based on "Last N Days" selection.  
+**Automation Status**: NOT AUTOMATED
+
+**Background**:
+- Before: Data was downloaded only for "Last N Days", causing Start dates to be relative to N days
+- After: Start displays an absolute date, even when "Last N Days" is shorter than the incident's actual start
+- Limit: Start is capped at max 15 days (the maximum supported range)
+
+- [ ] **Absolute Start Date Display**: Create an incident that started 10 days ago
+  - Set time filter to "Last 7 days"
+  - Verify incident Start date shows the absolute date (10 days ago), NOT a date relative to 7 days
+  - Verify the incident bar in the chart is trimmed to show only the portion within the 7-day window
+  - Verify tooltip shows the actual absolute start time
+
+- [ ] **API Call Pattern Verification**: Monitor network requests on initial page load
+  - Verify 15 query_range calls are made on initial page load (one per day)
+  - Verify the time ranges cover the full 15-day window regardless of "Last N Days" selection
+
+### 3.5 Data Integrity
+**NEW, NOT AUTOMATED, TODO COO 1.4**
 - [ ] Incident grouping by `group_id` works correctly
 - [ ] Values deduplicated across multiple time range queries
 - [ ] Component lists combined for same group_id