Testing GET /batteries

ApplicationTests.java

@Test
void shouldReturnAllBatteries() throws Exception {
    mockMvc
            .perform(get("/batteries/"))
            .andDo(print())
            .andExpect(status().isOk())
            .andExpect(jsonPath("$").isArray())
            .andExpect(jsonPath("$", Matchers.hasSize(H2Bootstrap.mockBatteries.size())));
}