Static Application Security Testing (SAST) and Dynamic Application Security Testing (DAST) are two distinct approaches to application security testing that complement each other, with SAST analyzing source code for vulnerabilities before deployment and DAST simulating external attacks on running applications. While they can find some overlapping risks, SAST excels at detecting code-related issues and is typically deployed earlier in the development lifecycle, resulting in lower costs to fix. DAST, on the other hand, finds vulnerabilities that manifest in runtime environments and requires redeployment after fixes are made. Other security testing methodologies like Interactive Application Security Testing (IAST) and Runtime Application Self-Protection (RASP) also offer complementary tools for application security testing.