In personality research, the distinction between state and trait is often made. States are momentary emotional reactions to internal and/or external triggers, such as physical, behavioral, cognitive and psychological reactions. Anger and sadness are examples of emotional states. Traits, on the other hand, are personality characteristics that are stable over time. Examples include Openness, Conscientiousness, Extraversion, Agreeableness and Emotional Stability, as described in Alva's personality test.

Even though personality assessments are designed to measure traits, it is impossible to completely remove the effect of states on the responses. For example, a study from 2014 showed that sadness may lead to increased neuroticism and decreased extraversion scores (Querengässer & Schindler, 2014). 

Statistically, the effect of state on personality scores can be thought of as part of the uncertainty in the measurement. Since the standard error of measurement (SEM) of most personality assessments is about 1 point on the Standard Ten scale (or 0.5 on the z-scale), it is to be expected that scores vary by 1-2 points between sessions, which is in part due to the effect of state on the scores.

See this article for a study we conducted to investigate the test-retest reliability of Alva's personality test.