Fix fits function to check that total values are non-negative (#189)

pkg/cloudprovider/fake/cloudprovider.go

@@ -78,7 +78,7 @@ func (c *CloudProvider) Create(ctx context.Context, machine *v1alpha5.Machine) (
 	instanceTypes := lo.Filter(lo.Must(c.GetInstanceTypes(ctx, &v1alpha5.Provisioner{})), func(i *cloudprovider.InstanceType, _ int) bool {
 		return reqs.Compatible(i.Requirements) == nil &&
 			len(i.Offerings.Requirements(reqs).Available()) > 0 &&
-			resources.Fits(resources.Merge(machine.Spec.Resources.Requests, i.Overhead.Total()), i.Capacity)
+			resources.Fits(machine.Spec.Resources.Requests, i.Allocatable())
 	})
 	// Order instance types so that we get the cheapest instance types of the available offerings
 	sort.Slice(instanceTypes, func(i, j int) bool {

pkg/utils/resources/resources.go

@@ -136,6 +136,12 @@ func Cmp(lhs resource.Quantity, rhs resource.Quantity) int {
 
 // Fits returns true if the candidate set of resources is less than or equal to the total set of resources.
 func Fits(candidate, total v1.ResourceList) bool {
+	// If any of the total resource values are negative then the resource will never fit
+	for _, quantity := range total {
+		if Cmp(resource.MustParse("0"), quantity) > 0 {
+			return false
+		}
+	}
 	for resourceName, quantity := range candidate {
 		if Cmp(quantity, total[resourceName]) > 0 {
 			return false