Address review feedback

- Fix NEWS.md to start with action verb "Fixed"
- Add unit test for extended R trajectory scenario

Co-Authored-By: Sebastian Funk <sebastian.funk@lshtm.ac.uk>

Author: sbfnk-bot

NEWS.md

@@ -2,7 +2,7 @@
 
 ## Bug fixes
 
-- A bug was fixed in `forecast_infections()` where the summary call to extract dates was using modified args instead of the original fit dimensions, causing a date-dimension mismatch when extending the R trajectory beyond the original observation period.
+- Fixed a bug in `forecast_infections()` where the summary call to extract dates was using modified args instead of the original fit dimensions, causing a date-dimension mismatch when extending the R trajectory beyond the original observation period.
 
 ## Breaking changes
 

tests/testthat/test-forecast-infections.R

@@ -173,3 +173,23 @@ test_that("get_predictions produces expected output with format = 'summary'", {
   expect_true("mean" %in% names(preds))
   expect_false("confirm" %in% names(preds))
 })
+
+test_that("forecast_infections works with R extended beyond original fit", {
+  skip_integration()
+  fixtures <- get_test_fixtures()
+  # Get the original R length from the fit
+ original_R_length <- nrow(
+    summary(fixtures$estimate_infections, type = "parameters", param = "R")
+  )
+  # Create an R vector longer than the original fit (extend by 10 days)
+  extended_R <- c(rep(NA_real_, original_R_length), rep(0.8, 10))
+  # This would fail before the fix due to date-dimension mismatch
+  sims <- forecast_infections(
+    fixtures$estimate_infections, R = extended_R, samples = 10
+  )
+  expect_equal(names(sims), c("samples", "summarised", "observations"))
+  expect_true(nrow(sims$samples) > 0)
+  # Verify get_samples works (this was part of the failing call chain)
+  samples <- get_samples(sims)
+  expect_s3_class(samples, "data.table")
+})