RPM Spec How to specify in package so that previous RPM is removed

Question:

What do I put in the foo.spec file so that the RPMs will remove the previous RPM before installing?

Description:

I have created a spec file that creates rpm's for a few packages that use the same source and provide the same service, each with a slightly different configuration. E.g. they each provide the same "capability"

Here's an example of the essentials that my .spec file looks like:

%define version     1234
%define name        foo
%define release     1
%define pkgname     %{name}-%{version}-%{release}

Name:               %{name}
Version:            %{version}
Release:            %{release}
Provides:           %{name}

%package one
Summary:            Summary for foo-one
Group:              %{group}
Obsoletes:          %{name} <= %{version}
Provides:           %{name} = %{version}

%description one
Blah blah blah

%package two
Summary:            Summary for foo-two
Group:              %{group}
Obsoletes:          %{name} <= %{version}
Provides:           %{name} = %{version}

%description two
Blah blah blah

# %prep, %install, %build and %clean are pretty simple 
# and omitted here for brevity sake

%files one
%defattr(-,root,root,-)
%{_prefix}/%{pkgname}

%files two
%defattr(-,root,root,-)
%{_prefix}/%{pkgname}

When I install the first one, it installs ok. I then remove the first one, and then install the second one, that works fine too.

I then install the first one, followed immediately by installing the second one, and they both install, one over the other, but, I was expecting that the second one would be removed before installing the second.

Example session:

# rpmbuild foo and copy rpms to yum repo

$ yum install foo-one
...
$ yum list installed|grep foo
foo-one.noarch           1234-1                @myrepo

$ yum install foo-two
...[Should say that it is removing foo-one, but does not]...

$ yum list installed|grep foo
foo-one.noarch           1234-1                @myrepo
foo-two.noarch           1234-1                @myrepo

$ rpm -q --provides foo-one
foo = 1234
foo-one = 1234-1

$ rpm -q --provides foo-two
foo = 1234
foo-two = 1234-1

What do I put in the foo.spec file so that the RPMs will remove the previous RPM before installing?

Thank you,

.dave.