How to form a relative clause with a 是 in it? I want to be able to translate sentences with complicated relative clauses specifying that two things are the same in a particular context. For example, "I take classes where the tests are conversations." My inclination is to say

我采取考试是谈话的课程。

or

我采取考试是谈话那个课程。

But something about these doesn't feel quite right. Are these ungrammatical, and why? Is there a better way?
Unlike in English, in Chinese, an attributive clause is not long in general. Instead, we prefer to a subject-detail stucture over the sentence-attributive cluase structure.

In your case, if you insist on an attributive, you can say


  我选的是考试（形式）是谈话的课程
  What I take is classes whose tests (forms) are conversations".


This is correct, however, more naturally, I would say:


  我选的课程，其(它的)考试形式是谈话。
  The classes I take, whose (their) test forms are conversations.


Here, you first propose a topic/subject - 我选的课程, and then you start explaining its details. This is how Chinese language organizes the sentence structure.

Notes: 


I think the verb "take" in your case means "to choose/pick/select/participate in". The verb "采取" (to adopt/use/take) generally precedes nouns like 方法(method)，措施(measure),方案(plan).
I think "考试形式(test forms)" sounds more natural.
pay attention to the word "其"，it's a formal word used like "which/whose" as in an attributive clause in English. You can use it as a pronoun in the cluase to avoid mentioning the subject repeatly.