test(aws): preserve requested-window SP coverage rates

providers/aws/recommendations/sp_coverage.go

@@ -38,22 +38,17 @@ type SPCoverageSummary struct {
 	// (no SP-eligible activity in the window) or Days==0; a fully covered
 	// window (OnDemandCost==0, covered>0) yields &100.0, not nil.
 	CoveragePct *float64
-	// CoveredUSDPerHour is the average SP-covered spend per hour over the
-	// window (total SpendCoveredBySavingsPlans / windowHours). Nil when
-	// Days==0.
+	// CoveredUSDPerHour normalizes reported SP-covered spend over the requested
+	// window, without adjusting for reporting completeness. Nil when Days==0.
 	CoveredUSDPerHour *float64
-	// OnDemandUSDPerHour is the average spend billed at on-demand rates per
-	// hour, i.e. the SP-eligible spend NOT covered by any Savings Plan.
-	// This is the uncovered portion (CE's OnDemandCost), not the eligible
-	// total - see EligibleUSDPerHour for the total. Nil when Days==0.
+	// OnDemandUSDPerHour normalizes reported uncovered SP-eligible spend over
+	// the same requested window. Nil when Days==0.
 	OnDemandUSDPerHour *float64
-	// EligibleUSDPerHour is the average total SP-eligible spend per hour:
-	// CoveredUSDPerHour + OnDemandUSDPerHour. Provided so consumers (the
-	// ladder sizing math) do not have to re-derive the coverage
-	// denominator. Nil when Days==0.
+	// EligibleUSDPerHour is CoveredUSDPerHour + OnDemandUSDPerHour, normalized
+	// over the requested window including zero-activity days. Nil when Days==0.
 	EligibleUSDPerHour *float64
-	// Days is the count of daily CE data points that had a non-nil Coverage
-	// block in the response. Zero means CE returned no data for the window.
+	// Days counts daily CE data points with a non-nil Coverage block.
+	// It does not indicate reporting completeness or change the rate divisor.
 	Days int
 }
 

providers/aws/recommendations/sp_coverage_window_test.go

@@ -0,0 +1,69 @@
+package recommendations
+
+import (
+	"context"
+	"strconv"
+	"testing"
+	"time"
+
+	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/service/costexplorer"
+	"github.com/aws/aws-sdk-go-v2/service/costexplorer/types"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestGetSPCoverageSummary_SparseWindowRates(t *testing.T) {
+	for _, mode := range []string{"omitted", "zero", "nil"} {
+		for _, paged := range []bool{false, true} {
+			t.Run(mode+"/paged="+strconv.FormatBool(paged), func(t *testing.T) {
+				periods := make([]types.SavingsPlansCoverage, 0, 30)
+				start := time.Now().UTC().AddDate(0, 0, -30)
+				for day := 0; day < 30; day++ {
+					if day >= 10 && mode == "omitted" {
+						continue
+					}
+					cost := "12"
+					if day >= 10 {
+						cost = "0"
+					}
+					period := types.SavingsPlansCoverage{
+						TimePeriod: &types.DateInterval{Start: aws.String(start.AddDate(0, 0, day).Format(time.DateOnly)), End: aws.String(start.AddDate(0, 0, day+1).Format(time.DateOnly))},
+						Coverage:   &types.SavingsPlansCoverageData{SpendCoveredBySavingsPlans: aws.String(cost), OnDemandCost: aws.String(cost)},
+					}
+					if day >= 10 && mode == "nil" {
+						period.Coverage = nil
+					}
+					periods = append(periods, period)
+				}
+				pages := []*costexplorer.GetSavingsPlansCoverageOutput{{SavingsPlansCoverages: periods}}
+				if paged {
+					pages = []*costexplorer.GetSavingsPlansCoverageOutput{
+						{SavingsPlansCoverages: periods[:5], NextToken: aws.String("second")},
+						{SavingsPlansCoverages: periods[5:]},
+					}
+				}
+				mock := &mockSPCE{coveragePages: pages}
+				got, err := NewClientWithAPI(mock, "us-east-1").GetSPCoverageSummary(context.Background(), "us-east-1", 30)
+				require.NoError(t, err)
+				require.NotNil(t, got.CoveredUSDPerHour)
+				require.NotNil(t, got.OnDemandUSDPerHour)
+				require.NotNil(t, got.EligibleUSDPerHour)
+				require.NotNil(t, got.CoveragePct)
+				assert.InDelta(t, 1.0/6, *got.CoveredUSDPerHour, 1e-9)
+				assert.InDelta(t, 1.0/6, *got.OnDemandUSDPerHour, 1e-9)
+				assert.InDelta(t, 1.0/3, *got.EligibleUSDPerHour, 1e-9)
+				assert.InDelta(t, 50, *got.CoveragePct, 1e-9)
+				wantDays := 10
+				if mode == "zero" {
+					wantDays = 30
+				}
+				assert.Equal(t, wantDays, got.Days)
+				assert.Len(t, mock.coverageInputs, len(pages))
+				if paged {
+					assert.Equal(t, "second", aws.ToString(mock.coverageInputs[1].NextToken))
+				}
+			})
+		}
+	}
+}