Conversation analysis (CA) has exerted influence both on second language (L2) classroom pedagogy (e.g., Barraja-Rohan A, Pritchard R, Beyond talk: a course in communication and conversation skills for intermediate adult learners of English. Western Metropolitan Institute of TAFE, Melbourne, 1997; Wong J, Waring HZ, Conversation analysis and second language pedagogy. Cambridge University Press, Cambridge, 2010; Betz E, Huth T, Die Unterrichtspraxis/Teaching German 47:140–163, 2014) and on areas of second language testing (LT) such as post hoc evaluation of oral-interview tests (e.g., Lazaraton A, Studies in language testing 14. Cambridge University Press, Cambridge, 2002; Ross S, J Pragmatics 39:2017–2044, 2007; Seedhouse P, Nakatsuhara F, The discourse of the IELTS speaking test: interactional design and practice. Cambridge University Press (English Profile Studies), Cambridge, 2018), oral role-play assessments (Okada Y, J Pragmatics 42:1647–1688, 2010; Kasper G, Ross SJ, Appl Linguis Rev 9:475–486, 2017) and a priori L2 test-construction efforts (Walters FS, Lang Test 24:155–183, 2007; Youn SJ, Lang Test 32:199–225, 2015). However, it may be argued that CA and LT lack sufficient paradigmatic overlap to make joint-contributions to L2 classroom instruction meaningful. For example, each has different research mandates, CA focusing on descriptions of interactional behavior with little interest in psycholinguistic processes (Markee N, Conversation analysis. Lawrence Erlbaum, Mahwah, 2000; Markee N, Kasper G, Mod Lang J 88:491–500, 2004), which is in contrast to LT’s oft-explicit theoretical focus (e.g., Messick S, Educational measurement. Collier Macmillan Publishers, London, 1989; Bachman L, Fundamental considerations in language testing. Oxford University Press, Oxford, 1990). Moreover, both fields approach the subject of language norms from differing perspectives, which is problematic in regard to effective L2 classroom instruction. As an attempt at a resolution to these matters, this chapter offers, first, a comparative analysis of how CA and LT each view these methodological and epistemological issues, with reference to test validity (e.g., Bachman LF, Palmer A, Language testing in practice. Oxford University Press, Oxford, 1996; Kane M, Educational measurement. Praeger, Westport, 2006). Following this, empirical data in the form of transcribed extracts from test responses to a CA-informed test (CAIT) of L2 oral proficiency will be examined. The aim will be to consider practical links between CA and LT and to offer a set of test-development principles possibly useful for L2 teachers interested in applying CA to their classroom assessments.