public static Map<String, String> resolveAll(Map<String, String> properties) {
    return resolveAll(System.getenv(), properties);
  }
@Test
  public void testEnvironmentSubstitutionWithMissingVar() {
    Map<String, String> result =
        EnvironmentUtil.resolveAll(ImmutableMap.of(), ImmutableMap.of("user-test", "env:USER"));

    assertThat(result)
        .as("Should not contain values with missing environment variables")
        .isEqualTo(ImmutableMap.of());
  }