fix(session-replay): Fix conversion of frame rate to time interval (#6623)

Author: philprime

CHANGELOG.md

@@ -50,6 +50,7 @@
   - Add layer class filtering for views used in multiple contexts (e.g., SwiftUI._UIGraphicsView)
   - Improve transform calculations for views with custom anchor points
   - Fix axis-aligned transform detection for optimized opaque view clipping
+- Fix conversion of frame rate to time interval for session replay (#6623)
 
 ### Improvements
 

Sources/Swift/Integrations/SessionReplay/SentrySessionReplay.swift

@@ -233,7 +233,7 @@ import UIKit
             return
         }
 
-        if now.timeIntervalSince(lastScreenShot) >= Double(1 / replayOptions.frameRate) {
+        if now.timeIntervalSince(lastScreenShot) >= 1.0 / Double(replayOptions.frameRate) {
             takeScreenshot()
             self.lastScreenShot = now
 

Tests/SentryTests/Integrations/SessionReplay/SentrySessionReplayTests.swift

@@ -577,6 +577,120 @@ class SentrySessionReplayTests: XCTestCase {
         XCTAssertTrue(SentrySessionReplay.shouldEnableSessionReplay(environmentChecker: environmentChecker, experimentalOptions: experimentalOptions))
     }
 
+    // MARK: - Frame Rate Tests
+
+    func testFrameRate_1FPS_takesScreenshotsAtCorrectInterval() {
+        // Arrange
+        let fixture = Fixture()
+        let options = SentryReplayOptions(sessionSampleRate: 1, onErrorSampleRate: 1)
+        options.frameRate = 1
+        let sut = fixture.getSut(options: options)
+        sut.start(rootView: fixture.rootView, fullSession: true)
+        
+        fixture.screenshotProvider.lastImageCall = nil
+        
+        // Act & Assert - advance by 0.9 seconds, screenshot should NOT be taken
+        fixture.dateProvider.advance(by: 0.9)
+        Dynamic(sut).newFrame(nil)
+        XCTAssertNil(fixture.screenshotProvider.lastImageCall, "Screenshot should not be taken before 1 second interval")
+        
+        // Act & Assert - advance to exactly 1.0 seconds, screenshot SHOULD be taken
+        fixture.dateProvider.advance(by: 0.1)
+        Dynamic(sut).newFrame(nil)
+        XCTAssertNotNil(fixture.screenshotProvider.lastImageCall, "Screenshot should be taken at 1 second interval for 1 FPS")
+    }
+
+    func testFrameRate_2FPS_takesScreenshotsAtCorrectInterval() {
+        // Arrange
+        let fixture = Fixture()
+        let options = SentryReplayOptions(sessionSampleRate: 1, onErrorSampleRate: 1)
+        options.frameRate = 2
+        let sut = fixture.getSut(options: options)
+        sut.start(rootView: fixture.rootView, fullSession: true)
+        
+        fixture.screenshotProvider.lastImageCall = nil
+        
+        // Act & Assert - advance by 0.4 seconds, screenshot should NOT be taken
+        fixture.dateProvider.advance(by: 0.4)
+        Dynamic(sut).newFrame(nil)
+        XCTAssertNil(fixture.screenshotProvider.lastImageCall, "Screenshot should not be taken before 0.5 second interval")
+        
+        // Act & Assert - advance to 0.5 seconds, screenshot SHOULD be taken
+        fixture.dateProvider.advance(by: 0.1)
+        Dynamic(sut).newFrame(nil)
+        XCTAssertNotNil(fixture.screenshotProvider.lastImageCall, "Screenshot should be taken at 0.5 second interval for 2 FPS")
+        
+        // Act & Assert - reset and test second screenshot
+        fixture.screenshotProvider.lastImageCall = nil
+        fixture.dateProvider.advance(by: 0.4)
+        Dynamic(sut).newFrame(nil)
+        XCTAssertNil(fixture.screenshotProvider.lastImageCall, "Screenshot should not be taken before another 0.5 seconds")
+        
+        fixture.dateProvider.advance(by: 0.1)
+        Dynamic(sut).newFrame(nil)
+        XCTAssertNotNil(fixture.screenshotProvider.lastImageCall, "Screenshot should be taken at next 0.5 second interval")
+    }
+
+    func testFrameRate_10FPS_takesScreenshotsAtCorrectInterval() {
+        // Arrange
+        let fixture = Fixture()
+        let options = SentryReplayOptions(sessionSampleRate: 1, onErrorSampleRate: 1)
+        options.frameRate = 10
+        let sut = fixture.getSut(options: options)
+        sut.start(rootView: fixture.rootView, fullSession: true)
+        
+        // Expected interval: 1.0 / 10.0 = 0.1 seconds
+        // Take first screenshot to establish baseline
+        fixture.dateProvider.advance(by: 0.1)
+        Dynamic(sut).newFrame(nil)
+        XCTAssertNotNil(fixture.screenshotProvider.lastImageCall, "First screenshot should be taken")
+        
+        fixture.screenshotProvider.lastImageCall = nil
+        
+        // Act & Assert - advance by 0.09 seconds, screenshot should NOT be taken
+        fixture.dateProvider.advance(by: 0.09)
+        Dynamic(sut).newFrame(nil)
+        XCTAssertNil(fixture.screenshotProvider.lastImageCall, "Screenshot should not be taken before 0.1 second interval")
+        
+        // Act & Assert - advance to reach 0.1 second interval, screenshot SHOULD be taken
+        fixture.dateProvider.advance(by: 0.01)
+        Dynamic(sut).newFrame(nil)
+        XCTAssertNotNil(fixture.screenshotProvider.lastImageCall, "Screenshot should be taken at 0.1 second interval for 10 FPS")
+    }
+
+    func testFrameRate_multipleScreenshots_respectsInterval() {
+        // Arrange
+        let fixture = Fixture()
+        let options = SentryReplayOptions(sessionSampleRate: 1, onErrorSampleRate: 1)
+        options.frameRate = 5
+        let sut = fixture.getSut(options: options)
+        sut.start(rootView: fixture.rootView, fullSession: true)
+        
+        // Expected interval: 1.0 / 5.0 = 0.2 seconds
+        var screenshotCount = 0
+        
+        // Act & Assert - take 5 screenshots over 1 second
+        // Each screenshot resets the timer, so we need to advance by the full interval each time
+        for i in 0..<5 {
+            // Advance by full interval
+            fixture.dateProvider.advance(by: 0.2)
+            Dynamic(sut).newFrame(nil)
+            
+            XCTAssertNotNil(fixture.screenshotProvider.lastImageCall, "Screenshot #\(i + 1) should be taken at \(Double(i + 1) * 0.2) seconds")
+            screenshotCount += 1
+            fixture.screenshotProvider.lastImageCall = nil
+            
+            // Advance by less than interval and verify no screenshot
+            if i < 4 { // Don't test after the last screenshot
+                fixture.dateProvider.advance(by: 0.1)
+                Dynamic(sut).newFrame(nil)
+                XCTAssertNil(fixture.screenshotProvider.lastImageCall, "No screenshot should be taken at \(Double(i + 1) * 0.2 + 0.1) seconds")
+            }
+        }
+        
+        XCTAssertEqual(screenshotCount, 5, "Should have taken exactly 5 screenshots in 1 second for 5 FPS")
+    }
+
     // MARK: - Helpers
 
     private func assertFullSession(_ sessionReplay: SentrySessionReplay, expected: Bool) {