Junit.framework does not exist

I'm sure this must be an ID-ten-T error, but I've Googled, experimented, and downloaded five different versions of junit, and I still can't crack it ...

I'm trying to compile a .java file that require the class junit.framework.Assert from the junit package (and several other packages, all of which I have successfully downloaded and installed). But when I download the junit package, there is no subdirectory of the directory junit called framework - there are only two subdirectories, one called 'tests' and the other called 'samples'. There is a directory called 'framework' beneath 'tests', but is doesn't contain a class called Assert.class - just AssertTest.class.

Yet the 'doc' directory contains documentation that states that junit.framework.Assert does indeed exist!

I have looked in org.junit (in the three junit4.x packages that I downloaded) - the same structure exists, but there is no class beginning with 'Assert' at all.

Any ideas?